Screw compressor

ABSTRACT

A screw compressor includes a first rotor provided with a helical groove, a second rotor meshing with the first rotor, and a rotor casing covering at least an outer periphery of the first rotor. The second rotor rotates together with the first rotor. The rotor casing defines a compression chamber in the helical groove together with the first rotor and the second rotor. A fluid is compressible in the compression chamber. At least one of the first rotor or the second rotor is provided with an oil supply passage connected to an oil supply port opened at a sliding surface of the rotor to supply a lubricant to the sliding surface.

TECHNICAL FIELD

The present invention relates to a screw compressor.

BACKGROUND ART

As a conventional compressor for compressing a fluid such as arefrigerant or air, a screw compressor having a first rotor comprised ofa screw rotor provided with helical grooves, and second rotors whichmesh with the first rotor and rotate together with the first rotor hasbeen used (see Patent document 1 below).

Patent Document 1 discloses a single-screw compressor including a screwrotor as a first rotor which is rotatably housed in a cylindrical wall,and gate rotors as second rotors which are arranged outside thecylindrical wall. Some of gates of each gate rotor enter the internalspace of the cylindrical wall through an opening formed therein to meshwith the screw rotor, so that the gate rotors rotate together with thescrew rotor. The cylindrical wall, the screw rotor, and the gatesmeshing with the screw rotor define a compression chamber in the helicalgrooves. When the screw rotor is driven by an electric motor to rotate,the gates meshing with the screw rotor are pushed to rotate the two gaterotors. When the position of the gate changes in the helical groove, thecapacity of the compression chamber decreases to compress the fluid.

In the conventional screw compressor described above, a lubricant isinjected toward the screw rotor from an oil supply port formed at apredetermined position of the cylindrical wall to supply the lubricantbetween sliding surfaces of two members, such as the screw rotor and thegate, or the screw rotor and the cylindrical wall, thereby lubricatingthe sliding surfaces, or sealing a minute gap, if any, formed betweenthe two members when they do not slide. This configuration keeps thesliding surfaces of the screw compressor from wearing or seizing, andblocks a high pressure fluid from leaking from the compression chamberdefined by the cylindrical wall, the screw rotor, and the gate.

CITATION LIST Patent Document

[Patent Document 1] Japanese Published Patent Application No.2009-197794

SUMMARY OF THE INVENTION Technical Problem

When the lubricant is injected toward the screw rotor from the oilsupply port formed at a predetermined position of the cylindrical wall,just like in the screw compressor described above, the lubricant doesnot reach the sliding surfaces in some cases when the injection amountof the lubricant is small. Therefore, the screw compressor describedabove requires the injection of a large amount of lubricant in order tosupply the lubricant to the sliding surfaces with reliability.

However, when a large amount of lubricant is injected into the helicalgrooves of the screw rotor, the lubricant can be reliably supplied tothe sliding surfaces, but power required for transporting the lubricantincreases. Further, when a large amount of lubricant is supplied intothe helical grooves of the screw rotor, an excess of the lubricantblocks the screw rotor from rotating, which increases power required forthe rotation of the screw rotor. When the screw compressor is improvedin speed and reduced in size, such an increase in the required power hasbeen a problem because the efficiency of the compressor remarkablydecreases.

In view of the foregoing, it is therefore an object of the presentinvention to provide a configuration of a screw compressor in which thelubricant can be reliably supplied to the sliding surfaces whilereducing the supply amount of the lubricant.

Solution to the Problem

A first aspect of the present disclosure is directed to a screwcompressor comprising: a first rotor (40) provided with a helical groove(41); a second rotor (50) which meshes with the first rotor (40) androtates together with the first rotor (40); a rotor casing (30) whichcovers at least an outer periphery of the first rotor (40), and definesa compression chamber (23) in the helical groove (41) together with thefirst rotor (40) and the second rotor (50), wherein a fluid iscompressed in the compression chamber (23), and at least one of thefirst rotor (40) or the second rotor (50) is provided with an oil supplypassage (5) which is connected to an oil supply port (4) opened at asliding surface (3) of the rotor (40, 50) to supply a lubricant to thesliding surface (3).

In the first aspect of the present disclosure, the oil supply passage(5) is formed in at least one of the rotors (40, 50), i.e., the firstrotor (40) and the second rotor (50) which mesh with each other androtate together, and the oil supply passage (5) is connected to the oilsupply port (4) opened at the sliding surface (3) of the rotor (40, 50)in which the oil supply passage (5) is formed. Thus, in the rotor (40,50) provided with the oil supply passage (5), the lubricant in the oilsupply passage (5) flows from the oil supply port (4) to the slidingsurface (3) to lubricate the sliding surface (3), or seal a gap, if any,between the sliding surface (3) and its counterpart sliding surface.

Further, in the first aspect of the present disclosure, unlike theconventional configuration in which the lubricant is injected from theoil supply port formed in a rotor casing which does not rotate, the oilsupply port (4) is opened at the sliding surface (3) of the rotor (40,50) that rotates, from which the lubricant is allowed to flow to thesliding surface (3). Therefore, the lubricant flowing from the oilsupply port (4) is rapidly spread over the rotating rotor (40, 50), andis rapidly supplied to the sliding surface (3) other than the slidingsurface (3) at which the oil supply port (4) is formed. Since the firstrotor (40) and the second rotor (50) mesh with each other and rotatetogether, the lubricant supplied to one of the rotors (40, 50) providedwith the oil supply passage (5) is rapidly spread to the other rotor(50, 40). Thus, the lubricant is quickly supplied to the sliding surface(3) of the other rotor (50, 40).

A second aspect of the present disclosure is an embodiment of the firstaspect. In the second aspect, a switching mechanism (6) switches the oilsupply passage (5) between a supply state in which the lubricant issupplied to the sliding surface (3) and a non-supply state in which nolubricant is supplied to the sliding surface (3).

In the second aspect of the present disclosure, the oil supply passage(5) can be switched between the supply state in which the lubricant issupplied from the oil supply passage (5) to the sliding surface (3), andthe non-supply state in which no lubricant is supplied from the oilsupply passage (5) to the sliding surface (3).

A third aspect of the present disclosure is an embodiment of the secondaspect. In the third aspect, the switching mechanism (6) is configuredto switch the oil supply passage (5) to the supply state by causing anoil supply source (94 c. 95 c) for supplying the lubricant to the oilsupply passage (5) to communicate with the oil supply passage (5) when arotational angle position of the rotor (40, 50) provided with the oilsupply passage (5) is in a predetermined angular range, and to switchthe oil supply passage (5) to the non-supply state by blocking the oilsupply source (94 c, 95 c) from the oil supply passage (5) when therotational angle position of the rotor (40, 50) is out of thepredetermined angular range.

In the third aspect of the present disclosure, when the rotational angleposition of the rotor (40, 50) provided with the oil supply passage (5)is in the predetermined angle range, the oil supply source (94 c. 95 c)communicates with the oil supply passage (5), and the oil supply passage(5) is switched to the supply state. When the rotational angle positionof the rotor (40, 50) is out of the predetermined angle range, the oilsupply source (94 c, 95 c) and the oil supply passage (5) are blockedfrom each other, and the oil supply passage (5) is switched to thenon-supply state.

A fourth aspect of the present disclosure is an embodiment of any one ofthe first to third aspects. In the fourth aspect, the first rotor (40)is a screw rotor (40) rotatably housed in a cylindrical wall (30)constituting the rotor casing (30), the second rotor (50) is agear-shaped gate rotor (50) having a plurality of flat gates (51) andarranged outside the cylindrical wall (30), some of the gates (51)entering a space inside the cylindrical wall (30) via an opening (39)formed in the cylindrical wall (30) and meshing with the screw rotor(40) so that the gate rotor (50) rotates together with the screw rotor(40), the oil supply passage (5) is formed in at least one of the gates(51) of the gate rotor (50), and the oil supply port (4) is a lateraloil supply port (63 b) opened at a side surface (51 a, 51 b) of the atleast one gate (51), the side surface (51 a, 51 b) serving as thesliding surface (3) which slides on the screw rotor (40).

In the fourth aspect of the present disclosure, the screw compressor (1)is configured as a single-screw compressor (1), and the gate rotor (50)which meshes with the screw rotor (40) rotates as the screw rotor (40)rotates. As a result, the position of the gate (51) in the helicalgroove (41) of the screw rotor (40) changes, the capacity of thecompression chamber (23) gradually decreases, and the fluid iscompressed. At this time, the lubricant in the oil supply passage (5)formed in the gate (51) of the gate rotor (50) flows from the lateraloil supply port (63 b) opened at the side surface (51 a, 51 b) of thegate (51) sliding on the screw rotor (40). Thus, the lubricant issupplied between the side surface (51 a, 51 b) of the gate (51) and thescrew rotor (40), thereby lubricating these sliding surfaces (3), orsealing a gap, if any, between these sliding surfaces (3). The lubricantsupplied between the side surface (51 a, 51 b) of the gate (51) and thescrew rotor (40) adheres to the screw rotor (40), and is spread towardthe outer periphery of the screw rotor (40) by the effect of acentrifugal force generated by the rotation of the screw rotor (40).Thus, the lubricant is supplied to a gap between the screw rotor (40)and the cylindrical wall (30) to seal the gap.

A fifth aspect of the present disclosure is an embodiment of the fourthaspect. In the fifth aspect, the lateral oil supply port (63 b) isopened at least at one of side surfaces (51 b), including the sidesurface (51 a, 51 b), on a rear side in a direction of rotation of theat least one gate (51).

When the screw rotor (40) rotates, the lateral face of the helicalgroove (41) of the screw rotor (40) pushes the gate (51) to rotate thegear-shaped gate rotor (50) meshing with the screw rotor (40).Specifically, the side surface (51 b) on the rear side in the rotationdirection of the gate (51) is the sliding surface which reliably slideson the screw rotor (40) and is pushed by the screw rotor (40), andtherefore, is probably worn through the sliding movement.

In the fifth aspect of the present disclosure, the lubricant is directlysupplied to the rear side surface (51 b) of the gate (51) in therotation direction from the oil supply passage (5). This makes itpossible to reliably supply the lubricant to the gap between the rearside surface (51 b) of the gate (51) in the rotation direction, which isprobably worn through the sliding movement, and the lateral faces of thehelical groove (41) of the screw rotor (40), thereby lubricating thesliding surfaces (3).

A sixth aspect of the present disclosure is an embodiment of the fourthor fifth aspect. In the sixth aspect, the oil supply passage (5) isconnected to a front oil supply port (63 c) opened at a front surface(51 c) of the at least one gate (51) facing the compression chamber(23).

The rotation of the gate rotor (50) causes the gate (51) to come in andout of the space inside the cylindrical wall (30) via the opening (39).In general, a gap is formed between the front surface (51 c) of the gate(51) and the cylindrical wall (30), but the front surface (51 c) of thegate (51) may slide on the cylindrical wall (30) when the gate rotor(50) thermally expands. If the gap is present between the front surface(51 c) of the gate (51) and the cylindrical wall (30), the lubricant maypossibly leak from the high pressure compression chamber (23) throughthe gap to a low-pressure space outside the cylindrical wall (30) inwhich the gate rotor (50) is disposed. Thus, the gap needs to be sealed.

In the sixth aspect of the present disclosure, the oil supply passage(5) is also connected to the front oil supply port (63 c) opened at thefront surface (51 c) of the gate (51). Therefore, in the gate (51) ofthe gate rotor (50), the lubricant in the oil supply passage (5) issupplied not only to the side surface (51 a, 51 b) that slide on thescrew rotor (40) but also to the front surface (51 c) that faces thecompression chamber (23). Thus, the lubricant is supplied between thefront surface (51 c) of the gate (51) and the cylindrical wall (30),thereby lubricating the front surface (51 c) and the cylindrical wall(30), or sealing a gap, if any, formed between the front surface (51 c)and the cylindrical wall (30).

A seventh aspect of the present disclosure is an embodiment of any oneof the fourth to sixth aspects. In the seventh aspect, the lateral oilsupply port (63 b) includes at least one lateral oil supply port (63 b)formed at a position closer to a base end of the at least one gate (51)than a center, of the at least one gate (51), in a radial direction ofthe gate rotor (50).

In the seventh aspect of the present disclosure, the lubricant in theoil supply passage (5) is supplied to a portion of the side surface (51a, 51 b) of the gate (51) sliding on the screw rotor (40) closer to thebase end than the center thereof in the radial direction. The lubricantsupplied to the portion of the side surface (51 a, 51 b) of the gate(51) closer to the base end is spread toward the distal end of the gate(51) by the effect of the centrifugal force generated by the rotation ofthe gate rotor (50).

An eighth aspect of the present disclosure is an embodiment of any oneof the fourth to seventh aspects. In the eighth aspect, the screwcompressor (1) further comprises a support member (55) supporting thegate rotor (50) from a rear side opposite to the compression 51 chamber(23), wherein an oil sump (62) to which the lubricant is supplied isformed between the support member (55) and a coupling portion (52) ofthe gate rotor (50) coupling base ends of the plurality of gates (51),and the oil supply passage (5) extends in a radial direction of the gaterotor (50) of the at least one gate (51), and has a base end connectedto the oil sump (62).

In the eighth aspect of the present disclosure, the oil supply passage(5) extends radially outward from the oil sump (62) closer to the baseend than the gate (51). In this configuration, the gate rotor (50)rotates to generate the centrifugal force, which causes the lubricant toenter and flow radially outward through the oil supply passage (5)extending from the oil sump (62) along the gate (51), and flow from thelateral oil supply port (63 b) to be supplied between the side surface(51 a, 51 b) of the gate (51) and the screw rotor (40).

A ninth aspect of the present disclosure is an embodiment of any one ofthe first to third aspects. In the ninth aspect, the oil supply passage(5) is formed in the first rotor (40), and the oil supply port (4) is anin-groove oil supply port (66 d) opened at an inner surface (42) of thehelical groove (41) serving as the sliding surface (3) of the firstrotor (40) sliding on the second rotor (50).

In the ninth aspect of the present disclosure, the oil supply passage(5) is formed in the first rotor (40), and connected to the in-grooveoil supply port (66 d) opened at the inner surface (42) of the helicalgroove (41) of the first rotor (40). In the first rotor (40) configuredin this manner, the lubricant in the oil supply passage (5) flows fromthe in-groove oil supply port (66 d) to the inner surface (42) of thehelical groove (41) which slides on the second rotor (50), therebylubricating the inner surface (42) of the helical groove, or sealing agap, if any, between the inner surface (42) and the second rotor (50)sliding on the inner surface (42). That is, in the ninth aspect of thepresent disclosure, unlike the conventional configuration in which thelubricant is injected from the oil supply port formed in the rotorcasing to be indirectly supplied to the inner surface (42) of thehelical groove of the first rotor (40), the lubricant is directlysupplied to the inner surface (42) of the helical groove serving as thesliding surface (3) from the in-groove oil supply port (66 d) opened atthe inner surface (42) of 10 o the helical groove of the first rotor(40).

Further, in the ninth aspect of the present disclosure, unlike theconventional configuration in which the lubricant is injected from theoil supply port formed in the rotor casing that does not rotate, the oilsupply port (4) is opened at the inner surface (42) of the helicalgroove of the first rotor (40) that rotates, from which the lubricant isallowed to flow to the inner surface (42). Therefore, the lubricantwhich has flowed from the in-groove oil supply port (66 d) is rapidlyspread over the rotating first rotor (40) by the effect of thecentrifugal force, and thus, the lubricant is quickly supplied to thesliding surfaces (3) other than the inner surface (42). Further, thelubricant supplied to the inner surface (42) of the helical groove ofthe first rotor (40) adheres to the second rotor (50) which meshes withand rotates with the first rotor (40), and is rapidly spread over thesecond rotor (50) by the effect of the centrifugal force. Thus, thelubricant is quickly supplied to the sliding surface (3) of the secondrotor (50).

A tenth aspect of the present disclosure is an embodiment of any one ofthe first to third aspects. In the tenth aspect, the oil supply passage(5) is formed in the first rotor (40), and the oil supply port (4) is anouter peripheral oil supply port (66 c) opened at an outer peripheralsurface (43) of the first rotor (40) serving as the sliding surface (3)of the first rotor (40) sliding on the rotor casing (30).

The outer peripheral surface (43) of the first rotor (40) provided withthe helical grooves (41) slides on the inner surface of the rotor casing(30) covering the outer periphery of the first rotor (40). Thus,lubrication is required to keep the outer peripheral surface (43) of thefirst rotor (40) and the inner surface of the rotor casing (30) fromseizing. On the other hand, when a gap is formed between the outerperipheral surface of the first rotor (40) and the inner surface of therotor casing (30), the gap needs to be sealed so that the high pressurefluid does not leak to the low pressure side.

In the tenth aspect of the present disclosure, the oil supply passage(5) is formed in the first rotor (40), and connected to the outerperipheral oil supply port (66 c) opened at the outer peripheral surface(43) of the first rotor (40) that slides on the rotor casing (30). Inthe first rotor (40) configured in this manner, the lubricant in the oilsupply passage (5) flows from the outer peripheral oil supply port (66c) to the outer peripheral surface (43) of the first rotor (40) thatslides on the inner surface of the rotor casing (30), therebylubricating the outer peripheral surface (43), or sealing a gap, if any,between the outer peripheral surface (43) and the inner surface of therotor casing (30).

Further, in the tenth aspect of the present disclosure, unlike theconventional configuration in which the lubricant is injected from theoil supply port formed in the rotor casing that does not rotate, the oilsupply port (4) is opened at the outer peripheral surface (43) of thefirst rotor (40) that rotates, from which the lubricant is allowed toflow to the outer peripheral surface (43). Therefore, the lubricant thathas flowed from the outer peripheral oil supply port (66 c) is rapidlyspread over the rotating first rotor (40), and is quickly supplied tothe sliding surfaces (3) other than the outer peripheral surface (43) atwhich the outer peripheral oil supply port (66 c) is formed. Since thefirst rotor (40) and the second rotor (50) mesh with each other torotate together, the lubricant supplied to the first rotor (40) israpidly spread to the second rotor (50). Thus, the lubricant can bequickly supplied to the sliding surface (3) of the second rotor (50).

An eleventh aspect of the present disclosure is an embodiment of theninth or tenth aspect. In the eleventh aspect, the first rotor (40) hasan oil sump (44) to which the lubricant is supplied, the oil sump (44)being formed at a position closer to a rotation axis of the first rotor(40) than a bottom face (42 c) of the helical groove (41), and the oilsupply passage (5) extends from the oil sump (44) toward an outerperiphery of the first rotor (40).

In the eleventh aspect of the present disclosure, the oil supply passage(5) extends from the oil sump (44) closer to the rotation axis than thebottom face (42 c) of the helical groove (41) of the first rotor (40)toward the outer periphery of the first rotor (40). In thisconfiguration, the first rotor (40) rotates to generate the centrifugalforce, which causes the lubricant to enter the oil supply passage (5)from the oil sump (44), flow toward the outer periphery of the firstrotor (40), and flow from the oil supply port (4) to be supplied to thesliding surface (3) of the first rotor (40).

Advantages of the Invention

According to the first aspect of the present disclosure, the oil supplypassage (5) is formed in at least one of the rotors (40, 50), i.e., thefirst rotor (40) and the second rotor (50) which mesh with each otherand rotate together, and the oil supply passage (5) is connected to theoil supply port (4) opened at the sliding surface (3) of the rotor (40,50) so that the lubricant is directly supplied from the oil supply port(4) to the sliding surface (3). This makes it possible to reliablysupply the lubricant to the sliding surface (3) of the rotor (40, 50).

Further, according to the first aspect of the present disclosure, unlikethe conventional configuration in which the lubricant is injected fromthe oil supply port formed in the rotor casing which does not rotate,the oil supply port (4) is opened at the sliding surface (3) of therotor (40, 50) that rotates, from which the lubricant is allowed to flowto the sliding surface (3). Therefore, the lubricant that has flowedfrom the oil supply port (4) is rapidly spread over the rotating rotor(40, 50), and can be quickly supplied to the sliding surface (3) otherthan the sliding surface (3) at which the oil supply port (4) is formed.Since the first rotor (40) and the second rotor (50) mesh with eachother and rotate together, the lubricant supplied to one of the rotors(40, 50) in which the oil supply passage (5) is formed is rapidly spreadto the other rotor (50, 40). Thus, the lubricant can be quickly suppliedto the sliding surface (3) of the other rotor (50, 40).

As described above, according to the first aspect of the presentdisclosure, the efficiency of the compressor is not lowered because itis unnecessary to increase the power for the transport of the lubricantand the power for the rotation of the first and second rotors (40, 50),unlike in the conventional configuration in which a large amount oflubricant is supplied. Supplying the lubricant in a small amount to atleast one of the sliding surface (3) of the first rotor (40) or thesliding surface (3) of the second rotor (50) makes it possible tolubricate the sliding surface (3) of each of the first rotor (40) andthe second rotor (50), or to seal the gap, if any, between the slidingsurface (3) and its counterpart sliding surface. That is, according tothe first aspect of the present disclosure, the sliding surfaces (3) ofthe first rotor (40) and the second rotor (50) can be kept from seizing,and the high pressure fluid can be blocked from leaking from thecompression chamber, even if the supply amount of the lubricant isreduced. Therefore, according to the first aspect of the presentdisclosure, the supply amount of the lubricant can be reduced withoutlowering the reliability of the screw compressor (1), which can improvethe compressor efficiency.

According to the second aspect of the present disclosure, the oil supplypassage (5) can be switched between the supply state in which thelubricant is supplied from the oil supply passage (5) to the slidingsurface (3), and the non-supply state in which no lubricant is suppliedfrom the oil supply passage (5) to the sliding surface (3). Thus, in asituation where the sliding surface (3) of the rotor (40, 50) providedwith the oil supply port (4) is not configured to slide constantly, theoil supply passage can be switched to the non-supply state to stop thesupply of the lubricant to the sliding surface (3) when the slidingsurface (3) does not slide and requires no lubrication. Therefore,according to the second aspect of the present disclosure, the lubricantcan be reliably supplied to the sliding surface (3) of the rotor (40,50), while reducing the amount of the lubricant supplied.

In the third aspect of the present disclosure, when the rotational angleposition of the rotor (40, 50) provided with the oil supply passage (5)is in the predetermined angle range, the oil supply source (94 c, 95 c)communicates with the oil supply passage (5), and the oil supply passage(5) is switched to the supply state. When the rotational angle positionof the rotor (40, 50) is out of the predetermined angle range, the oilsupply source (94 c, 95 c) and the oil supply passage (5) are blockedfrom each other, and the oil supply passage (5) is switched to thenon-supply state. Such a simple configuration of the third aspect of thepresent disclosure makes it possible to automatically switch the oilsupply passage (5) between the supply state and the non-supply statewhile the rotor (40, 50) provided with the oil supply passage (5) makesa single rotation.

According to the fourth aspect of the present disclosure, each of thegates (51) of the gate rotor (50) is provided with the oil supplypassage (5) which directly supplies the lubricant to the side surface(51 a, 51 b) which slide on the screw rotor (51) and need to belubricated and sealed by the lubricant. Thus, as compared to theconventional configuration in which the lubricant is injected into thehelical groove (41) to be indirectly supplied to the sliding surfaces(3) of the gate rotor (50) and the screw rotor (40), the lubricant canbe reliably supplied to the sliding surfaces (3) of the gate (51) andthe screw rotor (40) in a smaller amount, thereby lubricating thesliding surfaces (3), or sealing a gap, if any, between the slidingsurfaces (3). Moreover, the lubricant supplied in this manner to thesliding surfaces (3) of the screw rotor (40) and the gate (51) alsoadheres to the screw rotor (40), and is spread toward the outerperiphery of the screw rotor (40) by the effect of the centrifugal forcegenerated by the rotation of the screw rotor (40). Thus, the lubricantcan also be supplied to a gap between the screw rotor (40) and thecylindrical wall (30) to seal the gap.

As described above, according to the fourth aspect of the presentdisclosure, the efficiency of the compressor is not lowered because itis unnecessary to increase the power for the transport of the lubricantand the power for the rotation of the screw rotor (40), unlike in theconventional configuration in which a large amount of lubricant issupplied. Directly supplying the lubricant in a small amount to thesliding surfaces (3) of the gate (51) and the screw rotor (40) makes itpossible to lubricate the gate (51) and the screw rotor (40), and thescrew rotor (40) and the cylindrical wall (30), and to seal the gapbetween the gate (51) and the screw rotor (40), and the gap betweenscrew rotor (40) and the cylindrical wall (30), if any. That is,according to the fourth aspect of the present disclosure, the gate rotor(50) and the screw rotor (40) can be kept from seizing, and the highpressure fluid can be blocked from leaking from the compression chamber,even if the supply amount of the lubricant is reduced. Therefore,according to the fourth aspect of the present disclosure, the supplyamount of the lubricant can be reduced without lowering the reliabilityof the single-screw compressor (1), which can improve the compressorefficiency.

According to the fifth aspect of the present disclosure, the lateral oilsupply port (63 b) of the oil supply passage (5) is opened at least atthe side surface (51 b) of the gate (51) on the rear side in thedirection of rotation of the gate (51). The rear side surface (51 b) inthe rotation direction of the gate (51) is the sliding surface (3) whichreliably slides on the screw rotor (40) and is pressed by the screwrotor (40), and therefore, is probably worn through the slidingmovement. However, the lateral oil supply port (63 b) opened at the rearside surface (51 b) causes the lubricant to be reliably supplied betweenthe rear side surface (51 b) and the lateral face of the helical groove(41). This can protect the gate (51) and the screw rotor (40) from thesliding wear.

According to the sixth aspect of the present disclosure, the oil supplypassage (5) of the gate (51) is connected to not only the lateral oilsupply port (63 b) which is opened at the side surface (51 a, 51 b) thatslide on the screw rotor (40) of the gate (51), but also the front oilsupply port (63 c) which is opened at the front surface (51 c) of thegate (51). Thus, in the gate (51) of the gate rotor (50), the lubricantin the oil supply passage (5) can be supplied not only to the sidesurface (51 a, 51 b) that slide on the screw rotor (40), but also to thefront surface (51 c) that faces the compression chamber (23). As aresult, the lubricant is supplied between the front surface (51 c) ofthe gate (51) and the cylindrical wall (30) to lubricate the frontsurface (51 c) and the cylindrical wall (30), or seal a gap, if any,between the front surface (51 c) and the cylindrical wall (30). This cankeep the seizing caused by the sliding movement of the gate (51), andcan block the fluid from leaking from the high pressure compressionchamber (23) through the gap between the front surface (51 c) of thegate (51) and the cylindrical wall (30) to the low-pressure spaceoutside the cylindrical wall (30) where the gate rotor (50) is disposed.

According to the seventh aspect of the present disclosure, the lateraloil supply port (63 b) opened at the side surface (51 a, 51 b) of thegate (51) which slides on the screw rotor (40) includes at least onelateral oil supply port (63 b) formed at a position closer to the baseend of the gate (51) than the center thereof in the radial direction ofthe gate (51). The at least one lateral oil supply port (63 b) formed atthe position closer to the base end of the gate (51) than the centerthereof in the radial direction makes it possible to supply thelubricant to the base end of the side surface (51 a, 51 b) of the gate(51), and to easily spread the lubricant toward the distal end of theside surface (51 a, 51 b) of the gate (51) by utilizing the centrifugalforce. This configuration can minimize the number of the lateral oilsupply ports (63 b), and can further reduce the supply amount of thelubricant.

According to the eighth aspect of the present disclosure, the oil sump(62) is formed between the support member (55) supporting the gate rotor(50) and the coupling portion (52) of the gate rotor (50) coupling thebase ends of the gates (51), and an end of the oil supply passage (5)toward the base ends of the gates (51) is connected to the oil sump(62). That is, the oil supply passage (5) extends radially outward fromthe oil sump (62) along the corresponding gate (51). In thisconfiguration, the gate rotor (50) rotates to generate the centrifugalforce, which causes the lubricant in the oil sump (62) to enter and flowradially outward through the oil supply passage (5) in the gate (51),and flows from the lateral oil supply port (63 b) to be supplied betweenthe side surface (51 a, 51 b) of the gate (51) and the screw rotor (40).That is, this simple configuration can supply the lubricant between theside surface (51 a, 51 b) of the gate (51) and the screw rotor (40) byutilizing the centrifugal force generated by the rotation of the gaterotor (50).

According to the ninth aspect of the present disclosure, the oil supplypassage (5) is formed in the first rotor (40), and connected to thein-groove oil supply port (66 d) opened at the inner surface (42) of thehelical groove (41) of the first rotor (40), so that the lubricant isdirectly supplied from the in-groove oil supply port (66 d) to the innersurface (42) of the helical groove, which is the sliding surface (3)which slides on the second rotor (50). Thus, as compared to theconventional configuration in which the lubricant is injected from theoil supply port formed in the rotor casing to be indirectly supplied tothe inner surface (42) of the helical groove of the first rotor (40),the lubricant can be reliably supplied in a smaller amount to the innersurface (42) of the helical groove of the first rotor (40). Further, thein-groove oil supply port (66 d) is opened at the inner surface (42) ofthe helical groove of the first rotor (40) that rotates, from which thelubricant is allowed to flow to the inner surface (42). Thus, thelubricant that has flowed from the in-groove oil supply port (66 d) israpidly spread over the rotating first rotor (40), and the lubricant canalso be quickly supplied to the sliding surface (3) other than the innersurface (42). The lubricant supplied to the inner surface (42) of thehelical groove of the first rotor (40) also adheres to the second rotor(50) which meshes with and rotates with the first rotor (40), and israpidly spread over the second rotor (50) by the effect of thecentrifugal force. Thus, the lubricant can be quickly supplied to thesliding surface (3) of the second rotor (50).

According to the tenth aspect of the present disclosure, the oil supplypassage (5) is formed in the first rotor (40), and connected to theouter peripheral oil supply port (66 c) formed at the outer peripheralsurface (43) which slides on the rotor casing (30) of the first rotor(40), so that the lubricant is directly supplied from the outerperipheral oil supply port (66 c) to the outer peripheral surface (43)which is the sliding surface (3). This makes it possible to reliablysupply the lubricant to the outer peripheral surface (43) of the firstrotor (40) which slides on the inner surface of the rotor casing (30).

Further, according to the tenth aspect of the present disclosure, unlikethe conventional configuration in which the lubricant is injected fromthe oil supply port formed in the rotor casing that does not rotate, theoil supply port (4) is opened at the outer peripheral surface (43) ofthe first rotor (40) that rotates, from which the lubricant is allowedto flow to the outer peripheral surface (43). Therefore, the lubricantthat has flowed from the outer peripheral oil supply port (66 c) israpidly spread over the rotating first rotor (40), and is quicklysupplied to the sliding surface (3) other than the outer peripheralsurface (43) of the first rotor (40) at which the outer peripheral oilsupply port (66 c) is formed. Since the first rotor (40) and the secondrotor (50) mesh with each other and rotate together, the lubricantsupplied to the first rotor (40) is rapidly spread to the second rotor(50). Thus, the lubricant can be quickly supplied to the sliding surface(3) of the second rotor (50).

According to the eleventh aspect of the present disclosure, the oil sump(44) is formed at a position closer to the rotation axis of the firstrotor (40) than the bottom face (42 c) of the helical groove (41), and abase end of the oil supply passage (5) is connected to the oil sump(44). That is, the oil supply passage (5) extends from the oil sump (44)in the first rotor (40) toward the outer periphery. In thisconfiguration, the first rotor (40) rotates to generate the centrifugalforce, which causes the lubricant to enter the oil supply passage (5)from the oil sump (44), flow toward the outer periphery of the firstrotor (40), and flow from the oil supply port (4) to be supplied to thesliding surface (3) of the first rotor (40). That is, this simpleconfiguration can supply the lubricant to the sliding surface (3) of thefirst rotor (40) by utilizing the centrifugal force generated by therotation of the first rotor (40).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a general configuration of ascrew compressor according to a first embodiment.

FIG. 2 is a vertical sectional view illustrating the vicinity of acompression mechanism of the screw compressor.

FIG. 3 is a cross-sectional view illustrating the vicinity of thecompression mechanism of the screw compressor.

FIG. 4 is a perspective view illustrating a screw rotor and gate rotorstaken out of the screw compressor.

FIG. 5 is an enlarged view illustrating a right side portion of FIG. 3.

FIG. 6 is a perspective view illustrating a support member shown in FIG.5.

FIG. 7 is a vertical sectional view schematically illustrating the gaterotor and the screw rotor meshing with each other in an enlarged scale.

FIG. 8 is a sectional view illustrating a gate of the gate rotor and anarm of the support member in a helical groove of the screw rotor.

FIG. 9 is an enlarged view of a left side portion of FIG. 3.

FIGS. 10A to 10C are plan views respectively illustrating how acompression mechanism of a single-screw compressor is operated in asuction phase, a compression phase, and a discharge phase.

FIG. 11 is a cross-sectional view corresponding to FIG. 5, illustratinga screw compressor according to a second embodiment.

FIG. 12 is a cross-sectional view corresponding to FIG. 9, illustratingthe screw compressor of the second embodiment.

FIG. 13 is a vertical sectional view corresponding to FIG. 7,illustrating the screw compressor of the second embodiment.

FIG. 14 is a sectional view taken along line XIV-XIV in FIGS. 11 and 12.

FIG. 15 is a cross-sectional view illustrating the vicinity of acompression mechanism of a screw compressor of a third embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in detail withreference to the drawings.

First Embodiment

A screw compressor according to a first embodiment is a single-screwcompressor (1) provided in a refrigerant circuit for performing arefrigeration cycle, and compresses a refrigerant (fluid).

As shown in FIG. 1, in the single-screw compressor (1), a compressionmechanism (20) and an electric motor (15) driving the compressionmechanism are housed in a single casing (10). The single-screwcompressor (1) is configured as a semi-hermetic compressor.

The casing (10) has an outer wall (17) in the shape of a laterallyoriented cylinder. Space inside the casing (10) is divided into alow-pressure space (S1) located at one of longitudinal ends of the outerwall (17), and a high-pressure space (S2) located at the otherlongitudinal end. The casing (10) is provided with a suction pipeconnector (11) communicating with the low-pressure space (S1), and adischarge pipe connector (12) communicating with the high-pressure space(S2). Although not shown, a low pressure gas refrigerant flowing from anevaporator of a refrigerant circuit in a refrigeration apparatus, suchas a chiller system, flows into the low-pressure space (S1) through thesuction pipe connector (11). A compressed, high pressure gas refrigerantdischarged from the compression mechanism (20) into the high-pressurespace (S2) passes through the discharge pipe connector (12), and issupplied to a condenser of the refrigerant circuit.

Inside the outer wall (17) of the casing (10), the electric motor (15)is arranged in the low-pressure space (S1), and the compressionmechanism (20) is arranged between the low-pressure space (S1) and thehigh-pressure space (S2). The compression mechanism (20) has a driveshaft (21) coupled to the electric motor (15). The electric motor (15)of the single-screw compressor (1) is connected to a commercial powersupply (not shown). The electric motor (15) is supplied with analternating current from the commercial power supply, and rotates at apredetermined rotational speed.

Inside the outer wall (17) of the casing (10), an oil separator (16 a)is disposed in the high-pressure space (S2). The oil separator (16 a)separates a lubricant from the refrigerant discharged from thecompression mechanism (20). An oil reservoir chamber (16 b) for storingthe lubricant (lubricating oil) is formed in the high-pressure space(S2) below the oil separator (16 a). The lubricant separated from therefrigerant in the oil separator (16 a) flows downward and accumulatesin the oil reservoir chamber (16 b). The lubricant accumulated in theoil reservoir chamber (16 b) has high pressure which is substantiallyequal to the discharge pressure of the refrigerant.

As shown in FIGS. 2 and 3, the compression mechanism (20) includes acylindrical wall (rotor casing) (30), a single screw rotor (a firstrotor) (40), and two gate rotors (second rotors) (50) which mesh withthe screw rotor (40).

The cylindrical wall (30) is a cylinder-shaped thick wall, and isintegrated with the outer wall (17) to be part of the casing (10). Thescrew rotor (40) is rotatably housed in the cylindrical wall (30). Abearing holder (35) is fitted in a portion of the cylindrical wall (30)closer to the high-pressure space (S2) of the screw rotor (40).

A drive shaft (21) arranged coaxially with the screw rotor (40) isinserted through the screw rotor (40). The screw rotor (40) and thedrive shaft (21) are connected to each other by a key (22). The screwrotor (40) is driven to rotate in the casing (10) by the electric motor(15) disposed on the suction side of the screw rotor (40). One end ofthe drive shaft (21) is supported by the bearing holder (35) held by thecylindrical wall (30), via a bearing (36), and the other end isconnected to the electric motor (15).

As shown in FIG. 4, the screw rotor (40) is a metal member which issubstantially in the shape of a cylindrical column. The screw rotor (40)is rotatably fitted in the cylindrical wall (30). The screw rotor (40)has an outer diameter slightly smaller than an inner diameter of thecylindrical wall (30), and has an outer peripheral surface (43) whichslides on an inner peripheral surface (30 a) of the cylindrical wall(30) with a film of the lubricant present therebetween. That is, theouter peripheral surface (43) of the screw rotor (40) is configured as asliding surface (3) which slides on the inner peripheral surface (30 a)of the cylindrical wall (30). The screw rotor (40) has, on its outerperiphery, a plurality of helical grooves (41) (six grooves in thisembodiment) helically extending from one axial end of the screw rotor(40) to the other.

Each of the helical grooves (41) of the screw rotor (40) has a left endin FIG. 4 serving as a starting end, and a right end in FIG. 4 servingas a terminal end. A left end (an end on the suction side) of the screwrotor (40) in FIG. 4 is tapered. In the screw rotor (40) shown in FIG.4, the starting end of the helical groove (41) is opened at the taperedleft end face of the screw rotor (40), while the terminal end of thehelical groove (41) is not opened at a right end face of the screw rotor(40). An inner surface (42) of the helical groove (41) includes alateral face (42 a) on the front side in a direction of rotation of thescrew rotor (40), a lateral face (42 b) on the rear side in thedirection of rotation, and a bottom face (42 c) connecting the bottomends of the lateral faces (42 a, 42 b).

As shown in FIGS. 3 to 5 and FIGS. 7 to 9, each of the gate rotors (50)is a flat member made of a resin. Each gate rotor (50) has a pluralityof (eleven in this embodiment) gates (51), each of which is formed in arectangular plate shape, and a planar coupling portion (52) couplingbase ends of the plurality of gates (51). The gate rotor (50) is in theshape of a gear. The two gate rotors (50) are arranged outside thecylindrical wall (30) to be axially symmetric with respect to therotation axis of the screw rotor (40). The rotation axis of each gaterotor (50) is in a plane orthogonal to the center axis of the screwrotor (40).

Each of the gate rotors (50) is attached to a support member (55) madeof metal. As shown in FIG. 6, the support member (55) includes a base(56), arms (57), and a shaft (58). The base (56) is in the shape of arelatively thick disk. The arms (57) are provided in the same number(eleven in this embodiment) as the gates (51) of the gate rotor (50),and extend radially outward from an outer peripheral surface of the base(56). Each of the arms (57) abuts on a rear surface of an associated oneof the gates (51), thereby supporting the gate (51) from the rear side.The shaft (58) is in a rod shape and coupled to a center portion of thebase (56). The shaft (58) has a center axis which coincides with thecenter axis of the base (56). The shaft (58) penetrates through thecenter portion of the gate rotor (50), and is formed to extend forwardand rearward of the gate rotor (50). In this embodiment, the shaft (58)has a front shaft portion (58 a) which extends forward of the base (56)and is longer than a rear shaft portion (58 b) which extends rearward ofthe base (56).

The support members (55) to each of which the gate rotor (50) isattached are respectively housed in gate rotor chambers (90) definedinside the casing (10) to be adjacent to the cylindrical wall (30) (seeFIG. 3). Each of the gate rotor chambers (90) communicates with thelow-pressure space (S1).

As shown in an enlarged scale in FIGS. 5 and 9, first and second bearingholders (94, 95) formed as an integral part of the casing (10) areprovided in each of the gate rotor chambers (90). Each of the first andsecond bearing holders (94, 95) has a tubular portion (94 a, 95 a)having a cylindrical shape and a closed bottom, and a flange (94 b, 95b) formed around a base end of the tubular portion (94 a, 95 a). Thetubular portion (94 a, 95 a) of each of the first and second bearingholders (94, 95) is inserted into the gate rotor chamber (90) through anopening formed in the casing (10), and the flange (94 b, 95 b) is fixedto a portion around the opening of the casing (10). A bearing (92) isheld at a distal end of the tubular portion (94 a) of the first bearingholder (94), and a bearing (93) is held at a distal end of the tubularportion (95 a) of the second bearing holder (95).

The inside of the tubular portion (94 a) of the first bearing holder(94) serves as an oil sump (94 c) which stores the lubricant to besupplied to the bearing (92) at the distal end thereof. The inside ofthe second bearing holder (95) serves as an oil sump (95 c) which storesthe lubricant to be supplied to the bearing (93) at the distal endthereof. The oil sumps (94 c, 95 c) communicate with the oil reservoirchamber (16 b) formed in the high-pressure space (S2) through a passage(not shown). Each of the oil sumps (94 c, 95 c) stores the high pressurelubricant supplied from the oil reservoir chamber (16 b) through thepassage (not shown), and the lubricant reaches a sliding portion of thebearing (93, 94) to lubricate the sliding portion.

The support member (55) on the right of the screw rotor (40) and thesupport member (55) on the left of the screw rotor (3) in FIG. 3 areinverted from each other in the vertical direction. Specifically, thesupport member (55) on the right in FIG. 3 has the front shaft portion(58 a) located above the rear shaft portion (58 b) (see FIG. 5). Thesupport member (55) on the left in FIG. 3 has the front shaft portion(58 a) located below the rear shaft portion (58 b) (see FIG. 9). Thefront shaft portion (58 a) of each support member (55) is rotatablysupported by the second bearing holder (95) in each gate rotor chamber(90) via the bearing (93), and the rear shaft portion (58 b) of eachsupport member (55) is rotatably supported by the first bearing holder(94) in each gate rotor chamber (90) via the bearing (92).

The casing (10) is provided with an opening (13) through which anassembly of the gate rotor (50) and the support member (55) can beinserted into the inside of the gate rotor chamber (90) from the outsideof the casing (10), and a cover member (14) for covering the opening(13).

The cylindrical wall (30) has an opening (39) which allows each of thegate rotor chambers (90) to communicate with a screw rotor chamberformed inside the cylindrical wall (30). In each of the gate rotorchambers (90), the assembly of the gate rotor (50) and the supportmember (55) is disposed at a position where the gate (51) enters theinside of the cylindrical wall (30) through the opening (39) and mesheswith the screw rotor (40) (enters the helical groove (41)). An end faceof the cylindrical wall (30) forming the opening (39) and facing a frontsurface (51 c) of the gate (51) toward the compression chamber (23)serves as a sealing surface (39 a). The sealing surface (39 a) is a flatsurface extending in the axial direction of the screw rotor (40) alongthe outer periphery of the screw rotor (40). A distance between eachgate rotor (50) and the sealing surface (39 a) is set to be very small(e.g., 40 μm or less) so that the leakage of the fluid compressed in thecompression chamber (23) to the gate rotor chamber (90) is reduced asmuch as possible.

In the compression mechanism (20), a space surrounded by the innerperipheral surface (30 a) of the cylindrical wall (30), the innersurface (42) forming the helical groove (41) of the screw rotor (40),and the front surface (51 c) of the gate (51) of the gate rotor (50)functions as the compression chamber (23) for compressing the fluid. Anend of the helical groove (41) of the screw rotor (40) on the suctionside is opened toward the low-pressure space (S1), and this open endserves as a suction port (24) of the compression mechanism (20).

[Unloading Mechanism]

The single-screw compressor (1) is provided with an unloading mechanism(70, 80) which controls an operating capacity by performing an unloadingoperation of returning a portion of the gas in the course of thecompression to a low pressure side. The unloading mechanism (70, 80) iscomposed of slide valves (70) and a slide valve driving mechanism (80).

The slide valves (70) are respectively arranged in slide valve housings(31). As shown in FIG. 2, the slide valve housings (31) are formed attwo positions in the circumferential direction of the cylindrical wall(30). Each of the slide valves (70) is configured to be slidable in theaxial direction of the cylindrical wall (30), and faces the outerperipheral surface (43) of the screw rotor (40) when the slide valve(70) is inserted into an associated one of the slide valve housings(31). The slide valve (70) is fully opened when it moves to an endtoward the discharge side (the right side) in FIG. 2, or fully closedwhen it moves to an end toward the suction side.

In the casing (10), communication passages (32) are formed outside thecylindrical wall (30). The communication passages (32) are formed inone-to-one correspondence with the slide valve housings (31). Each ofthe communication passages (32) has one end opened in the low-pressurespace (S1), and the other end opened at an end on the suction side ofthe corresponding slide valve housing (31).

When the slide valves (70) slide toward the high-pressure space (S2)(i.e., to the right when the axial direction of the drive shaft (21) inFIG. 2 is regarded as the lateral direction), axial gaps (G) are formedbetween end faces of the slide valve housings (31) and end faces ofbypass opening degree regulating portions (71) of the slide valves (70).Each axial gap (G) forms, together with an associated one of thecommunication passages (32), a bypass passage (33) through which therefrigerant in the course of compression in the compression chamber (23)is returned to the low-pressure space (S1). That is to say, the bypasspassage (33) has one end communicating with the low-pressure space (S1)corresponding to the suction side of the compression chamber (23), andthe other end openable at the inner peripheral surface (30 a) of thecylindrical wall (30) where the compression in the compression chamber(23) is in progress. When the slide valves (70) are moved to change theopening degree of the bypass passages (33), a flow rate of therefrigerant returning from the position where the compression is inprogress to the low-pressure space varies. As a result, the capacity ofthe compression mechanism (20) varies.

Each slide valve (70) includes the bypass opening degree regulatingportion (71) for regulating the opening degree of the bypass passage(33), and a discharge opening regulating portion (72) for regulating anopening area of the discharge port (25) which is formed in thecylindrical wall (30) to allow the compression chamber (23) tocommunicate with the high-pressure space (S2). The slide valves (70) areslidable in the axial direction of the screw rotor (40). The dischargeopening regulating portion (72) of the slide valve (70) is configured tovary the opening area of the discharge port (25) in accordance with thechange in the position of the slide valve (70).

The slide valve driving mechanism (80) includes a cylinder tube (81), apiston (82) inserted in the cylinder tube (81), an arm (84) connected toa piston rod (83) of the piston (82), a connecting rod (85) connectingthe arm (84) and the slide valve (70), and a spring (86) for biasing thearm (84) to the right in FIG. 2 (in a direction in which the arm (84) isseparated from the casing (10)). The cylinder tube (81) and the piston(82) are components forming a hydraulic cylinder (hydropneumaticcylinder) (87). In this embodiment, one of axial end portions of thebearing holder (35) opposite to the screw rotor (40) is configured asthe cylinder tube (81). The hydraulic cylinder (87) is disposed acrossthe bearing (36) from the screw rotor (40), and is integrated with thebearing holder (35) holding the bearing (36).

Inside the bearing holder (35), a partition plate (38) is provided todefine a bearing chamber (C1) where the bearing (36) is held and acylinder chamber (C2) where the piston (82) of the hydraulic cylinder(87) is housed.

When the slide valve driving mechanism (80) is in the state shown inFIG. 2, the internal pressure of a space in the cylinder chamber (C2) onthe left of the piston (82) (space on the side of the piston (82) towardthe screw rotor (40)) is higher than the internal pressure of a space onthe right of the piston (82) (space on the side of the piston (82)toward the arm (84)). The slide valve driving mechanism (80) isconfigured to adjust the position of the slide valves (70) by regulatingthe internal pressure of the space on the right of the piston (82)(i.e., the gas pressure in the right space). Thus, although not shown, apassage for regulating the pressure in the right space of the piston(82) is formed in the bearing holder (35).

While the single-screw compressor (1) is in operation, a suctionpressure of the compression mechanism (20) acts on one of the axial endfaces of each slide valve (70) (i.e., the end face of the bypass openingdegree regulating portion (71)), and a discharge pressure of thecompression mechanism (20) acts on the other of the axial end faces ofeach slide valve (70). Consequently, during the operation of thesingle-screw compressor (1), a force pushing the slide valves (70)toward the low-pressure space (S1) constantly acts on the slide valves(70). Therefore, if the internal pressures of the left and right spacesof the piston (82) of the slide valve driving mechanism (80) vary, themagnitude of a force pulling the slide valves (70) back toward thehigh-pressure space (S2) varies, which changes the positions of theslide valves (70).

[Oil Supply Mechanism]

As shown in FIG. 3 and FIGS. 5 to 9, the single-screw compressor (1) isprovided with an oil supply mechanism (60) for supplying the lubricantto the side surfaces (51 a, 51 b) and front surface (51 c) of the gate(51) constituting the sliding surface (3) of the gate rotor (50). Inthis embodiment, the oil supply mechanism (60) is provided for each ofthe two gate rotors (50). In the following description, the oil supplymechanism (60) which supplies the lubricant to the sliding surface (3)of the gate rotor (50) on the right in FIG. 3, which is enlarged in FIG.5, will be referred to as a “right oil supply mechanism (60),” and theoil supply mechanism (60) which supplies the lubricant to the slidingsurface (3) of the gate rotor (50) on the left in FIG. 3, which isenlarged in FIG. 9, will be referred to as a “left oil supply mechanism(60).” Each of the two oil supply mechanisms (60) has an in-shaftcommunication passage (61), an oil sump (62), and a plurality ofgate-side oil supply passages (63) (oil supply passages (5)).

(Right Oil Supply Mechanism)

In the right oil supply mechanism (60) shown in FIGS. 5 and 6, thein-shaft communication passage (61) is formed inside the front shaftportion (58 a). The in-shaft communication passage (61) includes alongitudinal communication passage (61 a) and two lateral communicationpassages (61 b). The longitudinal communication passage (61 a) extendsstraight in the axial direction to pass through the center of the frontshaft portion (58 a) from one end to the other end thereof. Each of thetwo lateral communication passages (61 b) extends from the other end (anend toward the base (56)) of the longitudinal communication passage (61a) to the outside in a radial direction of the front shaft portion (58a), and is opened at the outer peripheral surface of the front shaftportion (58 a).

The oil sump (62) is formed between the coupling portion (52) couplingbase ends of the gates (51) and the base (56), of the support member(55), corresponding to the coupling portion (52). Specifically, a spacedefined by a groove (62 a) formed in the coupling portion (52) of thegate rotor (50) and a groove (62 b) formed in the base (56) of thesupport member (55) is configured as the oil sump (62). The groove (62a) in the gate rotor (50) and the groove (62 b) in the support member(55) are formed in an annular shape. As shown in FIG. 6, the groove (62b) formed in the base (56) of the support member (55) is formed in anannular shape to surround the outer periphery of the front shaft portion(58 a), and is opened at the front surface of the base (56) facing thegate rotor (50). The two lateral communication passages (61 b) of thein-shaft communication passage (61) are opened in the groove (62 b).This configuration allows the oil sump (62) to communicate with the oilsump (95 c) of the second bearing holder (95) above the front shaftportion (58 a) via the in-shaft communication passage (61).

The gate-side oil supply passages (63) are respectively formed in thegates (51) of the gate rotor (50). In this embodiment, the gate-side oilsupply passages (63) are formed in all of the eleven gates (51). Each ofthe gate-side oil supply passages (63) includes a body (53), a pluralityof lateral branches (54), and a front branch (59).

Specifically, as shown in FIG. 5, grooves (63 a) extending in the radialdirection of the gate rotor (50) are respectively formed in the rearsurfaces of the gates (51). The grooves (63 a) are closed by frontsurfaces of the arms (57) respectively supporting the gates (51) fromthe rear side. Space in each of the grooves (63 a) closed by the frontsurfaces of the arms (63) constitutes the body (53) of each of thegate-side oil supply passages (63). As shown in FIG. 7, the body (53) ofeach gate-side oil supply passage (63) extends radially from the baseend to distal end of the gate (51). A base end of the body (53) isconnected to the oil sump (62) formed between the coupling portion (52)coupling the base ends of the gates of the gate rotor (50) and the base(56) of the support member (55).

As shown in FIGS. 7 and 8, the lateral branches (54) are formed by holesextending from the body (53) in the circumferential direction of thegate rotor (50), and are connected to lateral oil supply ports (63 b)which are opened at side surfaces (51 a, 51 b) of the gate (51). Thelateral oil supply ports (63 b) constitute oil supply ports (4) forsupplying the lubricant to the side surfaces (51 a, 51 b), which are thesliding surfaces (3), of each gate (51). In this embodiment, each of thegates (51) is provided with four lateral branches (54) on the frontside, and four lateral branches (54) on the rear side, in the rotationdirection thereof. Thus, in this embodiment, four lateral oil supplyports (63 b) are opened at the front side surface (51 a) in the rotationdirection of the gate (51), and four lateral oil supply ports (63 b) areopened at the rear side surface (51 b). The four lateral oil supplyports (63 b) at the front side surface (51 a) and the four oil supplyports (63 b) at the rear side surface (51 b) are provided at positionscorresponding to each other. The four lateral oil supply ports (63 b) ateach side surface (51 a, 51 b) are arranged at substantially equalintervals from the base end to distal end of the gate (51). The diameterof each of the lateral oil supply ports (63 b) and lateral branches (54)is determined so that the lubricant flows in such an amount that allowsan oil film to be formed on the side surfaces (51 a, 51 b) of the gates(51), and that the lubricant is kept from scattering in the shape ofdroplets.

The number of lateral oil supply ports (63 b) and lateral branches (54)is not limited to four, but may be less than four, or more than four. Ina preferred embodiment, the diameter is changed in accordance with thenumber so that the lubricant flows in such an amount that allows an oilfilm to be formed on the side surfaces (51 a, 51 b) of the gates (51),and that the lubricant is kept from scattering in the shape of droplets.

As shown in FIG. 8, each of the side surfaces (51 a, 51 b) of the gate(51) which slides on the screw rotor (40) protrudes at a center portionin the thickness direction of the gate. Each of the protruding centerportion forms a seal line (L1, L2) which abuts on the correspondinglateral face (42 a, 42 b) of the helical groove (41) of the screw rotor(40). The lateral oil supply ports (63 b) are opened at the sidesurfaces (51 a, 51 b) of each gate (51) at a position forward of theseal line (L1. L2), that is, toward the compression chamber (23).

In this configuration, each of the gate-side oil supply passages (63) isconnected to the lateral oil supply ports (63 b) opened at the sidesurfaces (51 a, 51 b) of the gate (51) which slide on the screw rotor(40).

As shown in FIGS. 5, 7, and 8, the front branch (59) is a hole whichextends in a thickness direction of the gate (51) (a direction parallelto the axial direction of the gate rotor (50)) from the groove (63 a)(body (53)) extending in the radial direction of the gate rotor (50) ofthe gate (51), and is opened at the front surface (51 c). The frontbranch (59) is connected to a front oil supply port (63 c) opened at thefront surface (51 c) of the gate (51). The front oil supply port (63 c)constitutes an oil supply port (4) for supplying the lubricant to thefront surface (51 c), which is the sliding surface (3), of the gate(51). In this embodiment, the front branch (59) is provided for each ofthe plurality of gates (51). Thus, in this embodiment, a single frontoil supply port (63 c) is opened at each of the front surfaces (51 c) ofthe gates (51). In this embodiment, each of the front oil supply ports(63 c) is opened at a position further inward than the center of thefront surface (51 c) of the gate (51) in the radial direction. Thediameter of each of the front oil supply ports (63 c) and front branches(59) is determined so that the lubricant flows in such an amount thatallows an oil film to be formed on the front surfaces (51 c) of thegates (51), and that the lubricant is kept from scattering in the shapeof droplets. The number of front oil supply ports (63 c) and frontbranches (59) is not limited to one, but may be two or more. In apreferred embodiment, the diameter is changed in accordance with thenumber so that the oil film is formed on the front surfaces (51 c) ofthe gates (51).

In this configuration, each of the gate-side oil supply passages (63) isconnected to the front oil supply port (63 c) opened at the frontsurface (51 c) of the gate (51) facing the compression chamber (23).

As described above, in the right oil supply mechanism (60), the in-shaftcommunication passage (61), the oil sump (62), and the plurality ofgate-side oil supply passages (63), which are formed in the gate rotor(50) and the support member (55), form a lubricant passage which isbranched to have two or more outlets. The lubricant passage has an inletwhich is opened in the oil sump (95 c) of the second bearing holder (95)in which the high pressure lubricant flowing from the oil reservoirchamber (16 b) is accumulated. Although some of the plurality of lateraloil supply ports (63 b) and the front oil supply port (63 c), which arethe outlets of the lubricant passage, are opened in the compressionchamber (23), most of them are opened in the gate rotor chamber (90)communicating with the low-pressure space (S1). Therefore, due to thepressure difference between the inlet and outlets of the lubricantpassage, the high pressure lubricant in the oil sump (95 c) enters thelubricant passage, flows toward the outlets, and then flows to the sidesurfaces (51 a, 51 b) and front surface (51 c) of each gate (51).

(Left Oil Supply Mechanism)

In the left oil supply mechanism (60) shown in FIG. 9, the in-shaftcommunication passage (61) is formed inside the rear shaft portion (58b). The in-shaft communication passage (61) includes a longitudinalcommunication passage (61 a) and two lateral communication passages (61b). The longitudinal communication passage (61 a) extends straight inthe axial direction to pass through the center of the rear shaft portion(58 b) from one end to the other end thereof. Each of the two lateralcommunication passages (61 b) extends from the other end (an end towardthe base (56)) of the longitudinal communication passage (61 a) to theoutside in a radial direction of the rear shaft portion (58 b), and isopened at the outer peripheral surface of the rear shaft portion (58 b).

The oil sump (62) is formed between the coupling portion (52) couplingbase ends of the gate rotor (50) and the base (56), of the supportmember (55), corresponding to the coupling portion (52). Specifically, aspace defined by a groove (62 a) formed in the coupling portion (52) ofthe gate rotor (50) and a groove (62 b) formed in the base (56) of thesupport member (55) is configured as the oil sump (62). The groove (62a) in the gate rotor (50) and the groove (62 b) in the support member(55) are formed in an annular shape. The groove (62 b) formed in thebase (56) of the support member (55) is in an annular shape to surroundthe outer periphery of the rear shaft portion (58 b), and is opened atthe front surface of the base (56) facing the gate rotor (50). The twolateral communication passages (61 b) of the in-shaft communicationpassage (61) are opened in the groove (62 b). This configuration allowsthe oil sump (62) to communicate with the oil sump (94 c) of the firstbearing holder (94) above the rear shaft portion (58 b) via the in-shaftcommunication passage (61).

The gate-side oil supply passages (63) are respectively formed in thegates (51) of the gate rotor (50). In this embodiment, the gate-side oilsupply passages (63) are formed in all of the eleven gates (51). Each ofthe gate-side oil supply passages (63) includes a body (53), a pluralityof lateral branches (54), and a front branch (59).

Specifically, as shown in FIG. 9, grooves (63 a) extending in the radialdirection of the gate rotor (50) are formed in the rear surfaces of thegates (51). The grooves (63 a) are closed by front surfaces of the arms(57) respectively supporting the gates (51) from the rear side. Space ineach of the grooves (63 a) closed by the front surfaces of the arms (57)constitutes the body (53) of each of the gate-side oil supply passages(63). As shown in FIG. 7, the body (53) of each gate-side oil supplypassage (63) extends radially from the base end to distal end of thegate (51). A base end of the body (53) is connected to the oil sump (62)formed between the coupling portion (52) coupling the base ends of thegates of the gate rotor (50) and the base (56) of the support member(55).

As shown in FIGS. 7 and 8, the lateral branches (54) are formed by holesextending from the body (53) of the gate (51) in the circumferentialdirection of the gate rotor (50), and are connected to lateral oilsupply ports (63 b) which are opened at the side surfaces (51 a, 51 b)of the gate (51). The lateral oil supply ports (63 b) constitute oilsupply ports (4) for supplying the lubricant to the side surfaces (51 a,51 b), which are the sliding surfaces (3), of the gate (51). In thisembodiment, each of the gates (51) is provided with four lateralbranches (54) on the front side, and four lateral branches (54) on therear side, in the rotation direction thereof. Thus, in this embodiment,four lateral oil supply ports (63 b) are opened at the front sidesurface (51 a) in the rotation direction of the gate (51), and fourlateral oil supply ports (63 b) are opened at the rear side surface (51b). The four lateral oil supply ports (63 b) at the front side surface(51 a) and the four oil supply ports (63 b) at the rear side surface (51b) are provided at positions corresponding to each other. The fourlateral oil supply ports (63 b) at each side surface (51 a, 51 b) arearranged at substantially equal intervals from the base end to distalend of the gate (51). The diameter of each of the lateral oil supplyports (63 b) and lateral branches (54) is determined so that thelubricant flows in such an amount that allows an oil film to be formedon the side surfaces (51 a, 51 b) of the gates (51), and that thelubricant is kept from scattering in the shape of droplets.

The number of lateral oil supply ports (63 b) and lateral branches (54)is not limited to four, but may be less than four, or more than four. Ina preferred embodiment, the diameter is changed in accordance with thenumber so that the lubricant flows in such an amount that allows an oilfilm to be formed on the side surfaces (51 a, 51 b) of the gates (51),and that the lubricant is kept from scattering in the shape of droplets.

As shown in FIG. 8, each of the side surfaces (51 a, 51 b) of the gate(51) which slides on the screw rotor (40) protrudes at a center portionin the thickness direction of the gate. Each of the protruding centerportion forms a seal line (L1, L2) which abuts on the correspondinglateral face (42 a, 42 b) of the helical groove (41) of the screw rotor(40). The lateral oil supply ports (63 b) are opened at the sidesurfaces (51 a, 51 b) of each gate (51) at a position forward of theseal line (L1, L2), that is, toward the compression chamber (23).

In this configuration, each of the gate-side oil supply passages (63) isconnected to the lateral oil supply ports (63 b) opened at the sidesurfaces (51 a, 51 b) of the gate (51) which slide on the screw rotor(40).

As shown in FIGS. 7 to 9, the front branch (59) is a hole which extendsin a thickness direction of the gate (51) (a direction parallel to theaxial direction of the gate rotor (50)) from the groove (63 a) (body(53)) extending in the radial direction of the gate rotor (50) of thegate (51), and is opened at the front surface (51 c). The front branch(59) is connected to a front oil supply port (63 c) opened at the frontsurface (51 c) of the gate (51). The front oil supply port (63 c)constitutes an oil supply port (4) for supplying the lubricant to thefront surface (51 c), which is the sliding surface (3), of the gate(51). In this embodiment, the front branch (59) is provided for each ofthe plurality of gates (51). Thus, in this embodiment, a single frontoil supply port (63 c) is opened at each of the front surfaces (51 c) ofthe gates (51). In this embodiment, each of the front oil supply ports(63 c) is opened at a position further inward than the center of thefront surface (51 c) of the gate (51) in the radial direction. Thediameter of each of the front oil supply ports (63 c) and front branches(59) is determined so that the lubricant flows in such an amount thatallows an oil film to be formed on the front surfaces (51 c) of thegates (51), and that the lubricant is kept from scattering in the shapeof droplets. The number of front oil supply ports (63 c) and frontbranches (59) is not limited to one, but may be two or more. In apreferred embodiment, the diameter is changed in accordance with thenumber so that the oil film is formed on the front surfaces (51 c) ofthe gates (51).

In this configuration, each of the gate-side oil supply passages (63) isconnected to the front oil supply port (63 c) opened at the frontsurface (51 c) of the gate (51) facing the compression chamber (23).

As described above, in the left oil supply mechanism (60), the in-shaftcommunication passage (61), the oil sump (62), and the plurality ofgate-side oil supply passages (63), which are formed in the gate rotor(50) and the support member (55), form a lubricant passage which isbranched to have two or more outlets. The lubricant passage has an inletwhich is opened in the oil sump (94 c) of the first bearing holder (94)in which the high pressure lubricant flowing from the oil reservoirchamber (16 b) is accumulated. Although some of the plurality of lateraloil supply ports (63 b) and the front oil supply port (63 c), which arethe outlets of the lubricant passage, are opened in the compressionchamber (23), most of them are opened in the gate rotor chamber (90)communicating with the low-pressure space (S1). Therefore, due to thepressure difference between the inlet and outlets of the lubricantpassage, the high pressure lubricant in the oil sump (95 c) enters thelubricant passage, flows toward the outlets, and then flows to the sidesurfaces (51 a, 51 b) and front surface (51 c) of each gate (51).

—Operation—

When the electric motor (15) of the single-screw compressor (1) isactuated, the drive shaft (21) rotates, and the screw rotor (40) rotatesas well. As the screw rotor (40) rotates, the gate rotor (50) alsorotates, and the compression mechanism (20) repeats a suction phase, acompression phase, and a discharge phase. In the following description,the operation of the screw compressor (1) will be described, focusing onthe compression chamber (23) dotted in FIGS. 10A to 10C.

The compression chamber (23) dotted in FIG. 10A communicates with thelow-pressure space (S1). In this state, the gate (51) of the lower gaterotor (50) in FIG. 10A meshes with the corresponding helical groove (41)which defines the compression chamber (23). When the screw rotor (40)rotates, the gate (51) relatively moves within the helical groove (41)toward the terminal end of the helical groove (41), causing the capacityof the compression chamber (23) to gradually increase. As a result, thelow pressure gas refrigerant in the low-pressure space (S1) is suckedinto the compression chamber (23) through the suction port (24).

When the screw rotor (40) further rotates, the operation enters thestate of FIG. 10B. The compression chamber (23) dotted in FIG. 10B isfully closed. In this state, the gate (51) of the upper gate rotor (50)in FIG. 10B meshes with the corresponding helical groove (41) whichdefines the compression chamber (23), and the compression chamber (23)is partitioned from the low-pressure space (S1) by the gate (51). As thescrew rotor (40) rotates, the gate (51) relatively moves within thehelical groove (41) toward the terminal end of the helical groove (41),causing the capacity of the compression chamber (23) to graduallydecrease. As a result, the low pressure gas refrigerant in thecompression chamber (23) is gradually compressed.

When the screw rotor (40) further rotates, the operation enters thestate of FIG. 10C. The compression chamber (23) dotted in FIG. 10Ccommunicates with the high-pressure space (S2) through the dischargeport (25). In this state, when the gate (51) moves within the helicalgroove (41) toward the terminal end of the helical groove (41) with therotation of the screw rotor (40), the compressed, high pressurerefrigerant gas (high pressure gas refrigerant) is pushed out of thecompression chamber (23) to the high-pressure space (S2).

When the above operation is performed, the capacity of the compressionmechanism (20) is controlled using the slide valve (70). Although notspecifically described, when pushed to the leftmost position in FIG. 2,the slide valve (70) comes to the end where the slide valve (70) isfully closed (suction side). In this state, the capacity of thecompression mechanism (20) is maximized. When the slide valve (70) movesback to the right in FIG. 3, the tip end face of the slide valve (70)releases the axial gap (G), and the bypass passage (33) opens at theinner peripheral surface of the cylindrical wall (30). Then, a portionof the refrigerant gas sucked into the compression chamber (23) from thelow-pressure space (S1) returns to the low-pressure space (S1) from thecompression chamber (23) in the course of the compression phase via thebypass passage (33), and the rest of the refrigerant gas is compresseduntil the end of the compression phase and discharged to thehigh-pressure space (S2). Thus, the capacity of the compressionmechanism (20) decreases.

—Oil Supply Operation—

In this manner, when the screw rotor (40) and the two gate rotors (50)rotate to compress the refrigerant gas in the compression chamber (23),the two oil supply mechanisms (60) supply the lubricant to the slidingsurfaces (3) of the two gate rotors (50) and the screw rotor (40).

In the two oil supply mechanisms (60), as described above, the pressuredifference between the inlet and outlets of the lubricant passage formedby the in-shaft communication passage (61), the oil sump (62), and theplurality of gate-side oil supply passages (63) causes the lubricantsupplied to each oil sump (94 c, 95 c) from the oil reservoir chamber(16 b) to enter the lubricant passage, and flow toward the outlets.Specifically, the lubricant in the oil sump (94 c, 95 c) flows into thelongitudinal communication passage (61 a) of the in-shaft communicationpassage (61) inside the front shaft portion (58 a), diverges from thelongitudinal communication passage (61 a) to the two lateralcommunication passages (61 b), and eventually flows into the oil sump(62) (see FIGS. 5, 6, and 9). The lubricant that has reached the oilsump (62) flows into the plurality of gate-side oil supply passages (63)extending radially from the oil sump (62) by the effect of the drivingforce caused by the pressure difference described above and thecentrifugal force generated by the rotation of the gate rotor (50) andthe support member (55), and then flows radially outward in each of thegate-side oil supply passages (63) (see FIGS. 5 and 9). The lubricantflowing through the gate-side oil supply passages (63) flows to the sidesurfaces (51 a, 51 b) of the gate (51) from the plurality of lateral oilsupply ports (63 b), and to the front surface (51 c) of the gate (51)from the front oil supply port (63 c).

From the lateral oil supply ports (63 b) of each gate (51), thelubricant flows in such an amount that allows an oil film to be formedon the side surfaces (51 a, 51 b) of the gate (5). The lubricant thathas flowed from the plurality of lateral oil supply ports (63 b) isspread radially outward on the side surfaces (51 a, 51 b) of the gates(51) by the effect of the centrifugal force to form the oil film on eachof the side surfaces (51 a, 51 b).

As described above, as shown in FIG. 8, the lateral oil supply ports (63b) are opened at each of the side surfaces (51 a, 51 b) of the gate (51)at a position forward of the seal line (L1, L2) which abuts on thecorresponding lateral face (42 a, 42 b) of the helical groove (41) ofthe screw rotor (40), that is, further toward the compression chamber(23) than the seal line. Since the lateral oil supply ports (63 b) areprovided at such positions, the lubricant is supplied to a portion ofthe side surface (51 a, 51 b) forward of the seal line (L1, L2) of eachgate (51) in the traveling direction of the gate (51) when the gatetravels toward the compression chamber (23) in the helical groove (41)of the screw rotor (40). As a result, the lubricant is reliably suppliedto the seal line (L1, L2) of each gate (51) which slides on thecorresponding lateral face (42 a, 42 b) of the helical groove (41) ofthe screw rotor (40). This can lubricate the seal line (L1, L2), andachieve sealing at the seal line. This keeps the gas refrigerant in thehigh pressure compression chamber (23) from leaking from the gap betweenthe side surface (51 a, 51 b) of the gate (51) and the lateral face (42a. 42 b) of the helical groove (41) of the cylindrical wall (30) to thelow pressure compression chamber (23).

In this manner, the lubricant that has flowed from the lateral oilsupply ports (63 b) to the side surfaces (51 a, 51 b) of the gates (51)and supplied to the sliding surfaces (3) of the screw rotor (40) adheresto the screw rotor (40), and is spread to the outer periphery of thescrew rotor by the effect of the centrifugal force generated by therotation of the screw rotor (40). As a result, an oil film is formed onthe outer peripheral surface (43) of the screw rotor (40) between thehelical grooves (41), and the outer peripheral surface (43) and theinner peripheral surface (30 a) of the cylindrical wall (30) arelubricated and the gap between them is sealed. This keeps the screwrotor (40) from seizing, and blocks the gas refrigerant in the highpressure compression chamber (23) from leaking to the low pressurecompression chamber (23) through the gap between the outer peripheralsurface (43) of the screw rotor (40) and the inner peripheral surface(30 a) of the cylindrical wall (30).

On the other hand, the lubricant flows from the front oil supply port(63 c) of each of the gates (51) in such an amount that allows an oilfilm to be formed on the front surface (51 c) of the gate (51). Thelubricant that has flowed from the front oil supply port (63 c) isspread radially outward on the front surface (51 c) of the gate (51) bythe effect of the centrifugal force to form an oil film on the frontsurface (51 c). As described above, each of the front oil supply ports(63 c) is opened at a position inward of the center of the front surface(51 c) of each gate (51) in the radial direction (see FIG. 7).Therefore, the lubricant that has flowed from the front oil supply port(63 c) on the front surface (51 c) of the gate (51) is spread widelyoutward from the radially inward position.

The rotation of the gate rotor (50) causes each of the gates (51) tocome in and out of the cylindrical wall (30) via the opening (39) of thecylindrical wall (30). As described above, the lubricant flowed from thefront oil supply port (63 c) is widely spread over the front surface (51c) of each gate (51), and is supplied between the front surface (51 c)of the gate (51) and the sealing surface (39 a) of the cylindrical wall(30) facing each other. Thus, the lubricant lubricates the front surface(51 c) of the gate (51) and the sealing surface (39 a) of thecylindrical wall (30), which are the sliding surfaces, and seals a gaptherebetween. This keeps the gates (51) from seizing, and blocks the gasrefrigerant in the high pressure compression chamber (23) from leakingto the gate rotor chamber (90) through the gap between the front surface(51 c) of the gate (51) and the sealing surface (39 a) of thecylindrical wall (30).

Advantages of First Embodiment

According to the first embodiment, each of the gates (51) of the gaterotor (50) is provided with the gate-side oil supply passage (63)directly supplying the lubricant to the side surfaces (51 a. 51 b) whichslide on the screw rotor (51) and need to be lubricated and sealed bythe lubricant. Thus, as compared to the conventional configuration inwhich the lubricant is injected into the helical groove (41) to beindirectly supplied to the sliding surfaces (3) of the gate rotor (50)and the screw rotor (40), the lubricant can be reliably supplied to thesliding surfaces (3) of the gate (51) and the screw rotor (40) in asmaller amount, thereby lubricating the gate (51) and the screw rotor(40) and sealing the gap therebetween. Moreover, the lubricant suppliedin this manner to the sliding surfaces (3) of the screw rotor (40) andthe gate (51) also adheres to the screw rotor (40), and is spread towardthe outer periphery of the screw rotor (40) by the effect of thecentrifugal force generated by the rotation of the screw rotor (40).Thus, the lubricant can also be supplied to a gap between the screwrotor (40) and the cylindrical wall (30) to seal the gap.

As described above, in the present embodiment, the efficiency of thecompressor is not lowered because it is unnecessary to increase thepower for the transport of the lubricant and the power for the rotationof the screw rotor (40), unlike the conventional configuration in whicha large amount of lubricant is supplied. Directly supplying thelubricant in a small amount to the sliding surfaces (3) of the gate (51)and the screw rotor (40) makes it possible to lubricate the gate (51)and the screw rotor (40), and the screw rotor (40) and the cylindricalwall (30), and to seal the gap between the gate (51) and the screw rotor(40), and the gap between the screw rotor (40) and the cylindrical wall(30). That is, according to this embodiment, the gate rotor (50) and thescrew rotor (40) can be protected from the sliding wear, and a highpressure fluid can be blocked from leaking from the compression chamber,even if the supply amount of the lubricant is reduced. Therefore, in thepresent embodiment, the supply amount of the lubricant can be reducedwithout lowering the reliability of the single-screw compressor (1),which can improve the compressor efficiency.

According to the present embodiment, the gate-side oil supply passage(63) of the gate (51) is provided with not only the lateral oil supplyports (63 b) which are opened at the side surfaces (51 a, 51 b) thatslide on the screw rotor (40) of the gate (51), but also the front oilsupply port (63 c) which is opened at the front surface (51 c) of thegate (51). Therefore, in the gate (51) of the gate rotor (50), thelubricant in the gate-side oil supply passage (63) can be supplied notonly to the side surfaces (51 a, 51 b) that slide on the screw rotor(40), but also to the front surface (51 c) that faces the compressionchamber (23). As a result, the lubricant is supplied between the frontsurface (51 c) of the gate (51) sliding on the surface of thecylindrical wall (30), which lubricates these sliding surfaces, andseals a gap between them. This can keep the seizing caused by thesliding movement of the gate (51), and can block the fluid from leakingfrom the high pressure compression chamber (23) through the gap betweenthe front surface (51 c) of the gate (51) and the cylindrical wall (30)to the low-pressure space outside the cylindrical wall (30) where thegate rotor (50) is disposed.

Further, in the present embodiment, the oil sump (62) is formed betweenthe support member (55) supporting the gate rotor (50) and the couplingportion (52) of the gate rotor (50) coupling the base ends of the gates,and a base end of the gate-side oil supply passage (63) in the gate (51)is connected to the oil sump (62). That is, the gate-side oil supplypassage (63) extends radially outward from the oil sump (62) along thecorresponding gate (51). In this configuration, the gate rotor (50)rotates to generate the centrifugal force, which causes the lubricant inthe oil sump (62) to enter and flow radially outward through thegate-side oil supply passage (63) of the gate (51), and flow from thelateral oil supply ports (63 b). That is, this simple configuration cansupply the lubricant to the sliding surfaces (3) by utilizing thecentrifugal force generated by the rotation of the gate rotor (50).

Second Embodiment

In a second embodiment, the oil supply mechanism (60) and first andsecond bearing holders (94, 95) of the single-screw compressor (1) ofthe first embodiment are partially modified so that the lubricant issupplied intermittently as needed to the sliding surfaces (3) of thegate rotors (50).

[Oil Supply Mechanism]

Specifically, as shown in FIGS. 11 and 12, the single-screw compressorof the second embodiment has two oil supply mechanisms (60), each ofwhich includes a plurality of in-shaft communication passages (61), aplurality of oil sumps (62), and a plurality of gate-side oil supplypassages (63). In the second embodiment, eleven in-shaft communicationpassages (61), eleven oil sumps (62), and eleven gate-side oil supplypassages (63) are provided.

As shown in FIG. 11, the right oil supply mechanism (60) includes aplurality of in-shaft communication passages (61) formed inside thefront shaft portion (58 a). As shown in FIG. 12, the left oil supplymechanism (60) includes a plurality of in-shaft communication passages(61) formed inside the rear shaft portion (58 b). Each of the in-shaftcommunication passages (61) includes a longitudinal communicationpassage (61 a) and a lateral communication passage (61 b), and is formedin an L-shape.

As shown in FIG. 11, each of the longitudinal communication passages (61a) in the right oil supply mechanism (60) extends straight in the axialdirection to pass through an outer peripheral portion of the front shaftportion (58 a) from one end to the other end thereof. As shown in FIG.12, each of the longitudinal communication passages (61 a) in the leftoil supply mechanism (60) extends straight in the axial direction topass through an outer peripheral portion of the rear shaft portion (58b) from one end to the other end thereof.

As shown in FIG. 11, each of the lateral communication passages (61 b)in the right oil supply mechanism (60) extends outward in the radialdirection of the front shaft portion (58 a) from the other end (an endtoward the base (56)) of an associated one of the longitudinalcommunication passages (61 a), and is opened at an outer peripheralsurface of the front shaft portion (58 a). As shown in FIG. 12, each ofthe lateral communication passages (61 b) in the left oil supplymechanism (60) extends outward in the radial direction of the rear shaftportion (58 b) from the other end (an end toward the base (56)) of anassociated one of the longitudinal communication passages (61 a), and isopened at an outer peripheral surface of the rear shaft portion (58 b).

Thus, in each of the oil supply mechanisms (60) of the secondembodiment, the in-shaft communication passages (61) are formed in thesame number (eleven) as the gates (51) to be in one-to-onecorrespondence with the eleven gates (51). In each oil supply mechanism(60), the eleven in-shaft communication passages (61) are provided atequal intervals in the circumferential direction of the front shaftportion (58 a) or the rear shaft portion (58 b) so that each of theeleven lateral communication passages (61 b) extends in the direction ofextension of the corresponding gate (51).

In each oil supply mechanism (60), the plurality of oil sumps (62) areformed between a coupling portion (52) coupling base ends of the gatesof the gate rotor (50) and the base (56), of the support member (55),corresponding to the coupling portion (52). Specifically, a plurality ofgrooves (62 a) formed in the coupling portion (52) of the gate rotor(50) and a plurality of grooves (62 b) formed in the base (56) of thesupport member (55) form a plurality of spaces, which respectivelyconstitute the oil sumps (62). The grooves (62 a) of the gate rotor (50)and the grooves (62 b) of the support member (55) are formed in the samenumber (eleven) as the gates (51) to be in one-to-one correspondencewith the gates (51).

As shown in FIGS. 11 and 13, in the right oil supply mechanism (60), theeleven grooves (62 b) formed in the base (56) of the support member (55)extend radially outward from the outer peripheral surface of the frontshaft portion (58 a), and are opened at the front surface of the base(56) facing the gate rotor (50). As shown in FIGS. 12 and 13, in theleft oil supply mechanism (60), the eleven grooves (62 b) formed in thebase (56) of the support member (55) extend radially outward from theouter peripheral surface of the rear shaft portion (58 b), and areopened at the front surface of the base (56) facing the gate rotor (50).In each oil supply mechanism (60), each of the eleven lateralcommunication passages (61 b) of the in-shaft communication passage (61)is opened in an associated one of the grooves (62 b).

In each oil supply mechanism (60), the gate-side oil supply passages(63) are respectively formed in the gates (51) of the gate rotor (50).Also in the second embodiment, the gate-side oil supply passages (63)are formed in all of the eleven gates (51). In each of the oil supplymechanisms (60) of the second embodiment, the eleven gate-side oilsupply passages (63) are formed in one-to-one correspondence with theeleven oil sumps (62). Each of the gate-side oil supply passages (63)includes a body (53), a plurality of lateral branches (54), and a frontbranch (59).

Specifically, as shown in FIGS. 11 and 12, grooves (63 a) extending inthe radial direction of each gate rotor (50) are formed in the rearsurfaces of the gates (51). The grooves (63 a) formed in the gates (51)are formed in one to-one correspondence with the eleven grooves (62 a)formed in the coupling portion (52) of the gate rotor (50), and areintegrated with the corresponding grooves (62 a). The grooves (63 a)formed in the gates (51) are closed 251 by front surfaces of the arms(57) respectively supporting the gates (51) from the rear side. Space ineach of the grooves (63 a) closed by the front surfaces of the arms (57)constitutes the body (53) of each of the gate-side oil supply passages(63). As shown in FIG. 13, the body (53) of each gate-side oil supplypassage (63) extends radially from a base end to distal end of the gate(51). A base end of the body (53) is connected to the oil sump (62)formed between the coupling portion (52) coupling the base ends of thegates of the gate rotor (50) and the base (56), of the support member(55), corresponding to the coupling portion (52).

As shown in FIG. 13, in each of the oil supply mechanisms (60), thelateral branches (54) are formed by holes extending from each body (53)of the gate (51) in the circumferential direction of the gate rotor(50), and are connected to lateral oil supply ports (63 b), which areoil supply ports (4) opened at the side surfaces (51 a, 51 b) of thegate (51). Also in the second embodiment, each of the gates (51) isprovided with four lateral branches (54) on the front side, and fourlateral branches (54) on the rear side, in the rotation directionthereof. Thus, also in the second embodiment, four lateral oil supplyports (63 b) are opened at the front side surface (51 a) in the rotationdirection of the gate (51), and four lateral oil supply ports (63 b) areopened at the rear side surface (51 b). The four lateral oil supplyports (63 b) at the front side surface (51 a) and the four oil supplyports (63 b) at the rear side surface (51 b) are provided at positionscorresponding to each other. The four lateral oil supply ports (63 b) ateach side surface (51 a, 51 b) are arranged at substantially equalintervals from the base end to distal end of the gate (51). The diameterof each of the lateral oil supply ports (63 b) and lateral branches (54)is determined so that the lubricant flows in such an amount that allowsan oil film to be formed on the side surfaces (51 a, 51 b) of the gates(51), and that the lubricant is kept from scattering in the shape ofdroplets.

The number of lateral oil supply ports (63 b) and lateral branches (54)is not limited to four, but may be less than four, or more than four. Ina preferred embodiment, the diameter is changed in accordance with thenumber so that the lubricant flows in such an amount that allows an oilfilm to be formed on the side surfaces (51 a, 51 b) of the gates (51),and that the lubricant is kept from scattering in the shape of droplets.

Also in the second embodiment, as shown in FIG. 8, each of the sidesurfaces (51 a, 51 b) of the gate (51) which slides on the screw rotor(40) protrudes at a center portion in the thickness direction of thegate. Each of the protruding center portion forms a seal line (L1, L2)which abuts on the corresponding lateral face (42 a, 42 b) of thehelical groove (41) of the screw rotor (40). The lateral oil supplyports (63 b) are opened at the side surfaces (51 a. 51 b) of each gate(51) at a position forward of the seal line (L1, L2), that is, towardthe compression chamber (23).

In this configuration of the second embodiment, each of the gate-sideoil supply passages (63) in the oil supply mechanisms (60) is connectedto the lateral oil supply ports (63 b) opened at the side surfaces (51a, 51 b) of the gate (51) which slide on the screw rotor (40).

As shown in FIGS. 11, 12, and 8, the front branch (59) of the secondembodiment is a hole which extends in a thickness direction of the gate(51) (a direction parallel to the axial direction of the gate rotor(50)) from the groove (63 a) (body (53)) extending in the radialdirection of the gate rotor (50) of the gate (51), and is opened at thefront surface (51 c). The front branch (59) is connected to a front oilsupply port (63 c) which is the oil supply port (4) opened at the frontsurface (51 c) of the gate (51). Also in the second embodiment, thefront branches (59) are respectively provided for the plurality of gates(51), and thus, a single front oil supply port (63 c) is opened at eachof the front surfaces (51 c) of the gates (51). Each of the front oilsupply ports (63 c) is opened at a position further inward than thecenter of the front surface (51 c) of the gate (51) in the radialdirection. Also in the second embodiment, the diameter of each of thefront oil supply ports (63 c) and front branches (59) is determined sothat the lubricant flows in such an amount that allows an oil film to beformed on the front surfaces (51 c) of the gates (51), and that thelubricant is kept from scattering in the shape of droplets. The numberof front oil supply ports (63 c) and front branches (59) is not limitedto one, but may be two or more. In a preferred embodiment, the diameteris changed in accordance with the number so that the oil film is formedon the front surfaces (51 c) of the gates (51).

In this configuration of the second embodiment, the gate-side oil supplypassages (63) in each of the oil supply mechanisms (60) are connected tothe front oil supply ports (63 c) each of which is opened at the frontsurface (51 c) of the gate (51) facing the compression chamber (23).

Thus, in each of the oil supply mechanisms (60) of the secondembodiment, the plurality of in-shaft communication passages (61), theplurality of oil sumps (62), and the plurality of gate-side oil supplypassages (63), which are formed in the gate rotor (50) and the supportmember (55), form a plurality of lubricant passages.

[Bearing Holder]

As shown in FIGS. 11 and 12, in the second embodiment, each of the firstand second bearing holders (94, 95) has a tubular portion (94 a, 95 a)having a cylindrical shape and a closed bottom, a flange (94 b, 95 b)formed around a base end of the tubular portion (94 a, 95 a), and aclosing portion (94 d, 95 d). The tubular portions (94 a, 95 a) and theflanges (94 b, 95 b) are configured in the same manner as those of thefirst embodiment.

As shown in FIG. 11, in the right oil supply mechanism (60), the closingportion (95 d) of the second bearing holder (95) protrudes downward froman inner bottom surface of the tubular portion (95 a), and abuts on atop surface of the front shaft portion (58 a) of the support member (55)by a lower end thereof, thereby closing inlets of some of the elevenin-shaft communication passages (61) (inlets of the longitudinalcommunication passages (61 a)) formed inside the front shaft portion (58a) of the support member (55). As shown in FIG. 12, in the left oilsupply mechanism (60), the closing portion (94 d) of the first bearingholder (94) protrudes downward from an inner bottom surface of thetubular portion (94 a), and abuts on a top surface of the rear shaftportion (58 b) by a lower end thereof, thereby closing inlets of some ofthe eleven in-shaft communication passages (61) (inlets of thelongitudinal communication passages (61 a)) formed inside the rear shaftportion (58 b) of the support member (55).

In the second embodiment, as shown in FIG. 14, in each of the oil supplymechanisms (60), the closing portion (94 d, 95 d) of the bearing holder(194, 95) is configured to keep four of the inlets (61 a-1 to 61 a-11)of the eleven in-shaft communication passages (61) in the front shaftportion (58 a) or the rear shaft portion (58 b) closer to the screwrotor (40) open, and close the remaining seven inlets. With the closingportion (94 d, 95 d) formed in this manner, the oil sump (94 c, 95 c)formed in each of the first and second bearing holders (94, 95) isformed to have a wider portion on the side closer to the screw rotor(40), and a narrower portion on the other side.

Note that the front shaft portion (58 a) or the rear shaft portion (58b) in which the in-shaft communication passages (58) are formed rotatesin accordance with the rotation of the gate rotors (50), but the closingportion (94 d. 95 d) is fixed and does not rotate. Therefore, the inlets(61 a-1 to 61 a-11) of the in-shaft communication passages (61) to beclosed by the closing portions (94 d, 95 d) change in accordance withthe rotational angle position of the gate rotor (50).

For example, when the gate rotor (50) is at the rotational angleposition shown in FIG. 14, the closing portion (94 d, 95 d) closes thefifth to eleventh inlets (61 a-5 to 61 a-11), while keeping the first tofourth inlets (61 a-1 to 61 a-4) open. Thus, the first to fourth inlets(61 a-1 to 61 a-4) are opened to the oil sump (94 c, 95 c). When thegate rotor (50) moves in the direction of the arrow and its rotationalangle position changes, the closing portion (94 d, 95 d) closes thefourth to tenth inlets (61 a-4 to 61 a-10), while keeping the first tothird inlets (61 a-1 to 61 a-3) and the eleventh inlet (61 a-11) open.Thus, the first to third inlets (61 a-1 to 61 a-3) and the eleventhinlet (61 a-11) are opened in the oil sump (94 c, 95 c). As describedabove, in the second embodiment, the inlets (61 a-1 to 61 a-11) of thein-shaft communication passage (61) to be closed by the closing portion(94 d. 95 d) sequentially change as the rotational angle position of thegate rotor (50) changes.

The in-shaft communication passage (61) whose inlet is closed by theclosing portion (94 d, 95 d) is blocked from the oil sump (94 c. 95 c).Thus, no lubricant flows into this in-shaft communication passage fromthe oil sump (94 c, 95 c). Thus, no lubricant flows into the oil sump(62) and the gate-side oil supply passage (63) which are sequentiallyconnected to the in-shaft communication passage (61) whose inlet isclosed. That is, the oil sump (94 c, 95 c), which is the oil supplysource supplying the lubricant to the gate-side oil supply passage (63),is blocked from the gate-side oil supply passage (63). This brings thegate-side oil supply passage (63) into the non-supply state in which nolubricant is supplied to the side surfaces (51 a, 51 b) and frontsurface (51 c) of the gate (51), which are the sliding surfaces (3) ofthe gate rotor (50). On the other hand, the lubricant in the oil sump(94 c, 95 c) flows into the in-shaft communication passage (61) whoseinlet is not closed by the closing portion (94 d, 95 d) and is opened inthe oil sump (94 c, 95 c), and also into the oil sump (62) and thegate-side oil supply passage (63) which are sequentially connected tothe in-shaft communication passage (61). That is, the oil sump (94 c, 95c), which is the oil supply source supplying the lubricant to thegate-side oil supply passage (63), communicates with the gate-side oilsupply passage (63). This brings the gate-side oil supply passage (63)into the supply state in which the lubricant is supplied to the sidesurfaces (51 a, 51 b) and front surface (51 c) of the gate (51), whichare the sliding surfaces (3) of the gate rotor (50).

As can be seen, in the second embodiment, each of the oil supplymechanisms (60) includes the in-shaft communication passages (61) andthe oil sumps (62) which are individually connected to the gate-side oilsupply passages (63). Further, the closing portion (94 d. 95 d) isprovided to close some of the inlets (61 a-1 to 61 a-11) of the in-shaftcommunication passages (11). The inlets (61 a-1 to 61 a-11) of theinter-shaft communication passage (61) to be closed by the closingportion (94 d, 95 d) are changed in accordance with the rotation of thegate rotor (50). In this configuration, when the rotational angleposition of the gate rotor (50) is in a predetermined angular range A1to A11, the gate-side oil supply passages (63) are in the supply statein which the gate-side oil supply passages (63) communicate with the oilsump (94 c, 95 c) and supply the lubricant to the sliding surfaces (3).When the rotational angle position of the gate rotor (50) is out of thepredetermined angular range A1 to A11, the gate-side oil supply passages(63) are in the non-supply state in which the gate-side oil supplypassages (63) are blocked from the oil sump (94 c, 95 c) and supply nolubricant to the sliding surfaces (3). Thus, in each of the oil supplymechanisms (60) configured in this manner, the plurality of in-shaftcommunication passages (61), the plurality of oil sumps (62), and theclosing portion (94 d, 95 d) constitute a switching mechanism (6) forswitching the gate-side oil supply passages (63) between the supplystate and the non-supply state.

Advantages of Second Embodiment

According to the configuration of the second embodiment described above,the gate-side oil supply passages (63) can be switched between thesupply state in which the lubricant is supplied from the gate-side oilsupply passages (63) to the sliding surfaces (3), and the non-supplystate in which no lubricant is supplied from the gate-side oil supplypassages (63) to the sliding surfaces (3). Thus, in a situation wherethe sliding surfaces (3) of the gate rotor (50) (in this embodiment, theside surfaces (51 a, 51 b) and front surface (51 c) of the gate (51))provided with the lateral oil supply ports (63 b) and the front oilsupply port (63 c), which are the oil supply ports (4), are notconfigured to slide constantly, the gate-side oil supply passages (63)can be switched to the non-supply state to stop the supply of thelubricant to the sliding surfaces (3) when the sliding surfaces do notslide and require no lubrication. Therefore, according to the secondembodiment, the lubricant can be reliably supplied to the slidingsurfaces (3) of the gate rotors (50), while reducing the supply amountof the lubricant.

Specifically, for example, the switching mechanism (6) is configured toswitch the gate-side oil supply passage (63) formed in each gate (51) tothe supply state when the front surface (51 c) of the gate (51) facesthe sealing surface (39 a) of the cylindrical wall (30) and when theside surfaces (51 b, 51 c) of the gate (51) face the inner surface (42)of the helical groove of the screw rotor (40), and to switch thegate-side oil supply passage (63) to the non-supply state when the gate(51) does not face the cylindrical wall (30) or the screw rotor (40). Inthis configuration, when the gate (51) slides on the cylindrical wall(30) and the screw rotor (40), the sliding surfaces (3) can belubricated. When the gate (51) does not slide on the cylindrical wall(30) and the screw rotor (40) and forms a gap between the gate (51) andthe cylindrical wall (30) and the screw rotor (40), the gap can besealed. On the other hand, when the gate (51) does not face thecylindrical wall (30) or the screw rotor (40), no lubricant is suppliedto the sliding surfaces (3) from the gate-side oil supply passages (63).This can reduce the supply amount of the lubricant.

In the second embodiment, as described above, when the rotational angleposition of the gate rotor (50) is in the predetermined angular range A1to A11, the switching mechanism (6) switches the gate-side oil supplypassages (63) to the supply state in which the gate-side oil supplypassages (63) communicate with the oil sump (95 c, 94 c) to supply thelubricant to the sliding surfaces (3). When the rotational anglepositions of the gate rotor (50) is out of the predetermined angularrange A1 to A11, the switching mechanism (6) switches the gate-side oilsupply passages (63) to the non-supply state in which the gate-side oilsupply passages (63) are blocked from the oil sump (95 c, 94 c) andsupply no lubricant to the sliding surfaces (3). Such a simpleconfiguration of the second embodiment makes it possible toautomatically switch the gate-side oil supply passages (63) between thesupply state and the non-supply state while the gate rotor (50) makes asingle rotation.

Third Embodiment

In a third embodiment, the single-screw compressor (1) of the firstembodiment is modified such that the oil supply mechanism (60) providedfor each of the two gate rotors (50) is provided for the screw rotor(40) which meshes with the two gate rotors (50).

[Oil Supply Mechanism]

Specifically, as shown in FIG. 15, the single-screw compressor of thethird embodiment has the oil supply mechanism (60) which is formedinside the screw rotor (40) and includes a plurality of axial passages(65) and a plurality of screw-side oil supply passages (66) (oil supplypassages (5)).

The plurality of axial passages (65) is formed at a position closer tothe rotation axis than the bottom faces (42 c) of the helical grooves(41) of the screw rotor (40). In the third embodiment, six axialpassages (65) are formed, and are arranged at equal intervals on anouter periphery of the rotation axis of the screw rotor (40). Each axialpassage (65) is formed by a hole extending in the direction of therotation axis inside the screw rotor (40). A discharge end (a right endin FIG. 2) of each axial passage (65) is opened at an end face (rightend face in FIG. 2) of the screw rotor (40) on the discharge side. Asuction end (a left end in FIG. 2) of each axial passage (65) does notreach an end face (a left end face in FIG. 2) of the screw rotor (40).The discharge end of each axial passage (65) is opened in a space wherethe high pressure lubricant that has lubricated the bearing (36) of thebearing holder (35) for rotatably supporting the drive shaft (21), forexample, is accumulated. This configuration causes the high pressurelubricant to flow into the plurality of axial passages (65), and causesthe axial passages (65) to serve as oil sumps in which the high pressurelubricant is accumulated.

The plurality of screw-side oil supply passages (66) is formed such thatat least one screw-side oil supply passage (66) extends from anassociated one of the axial passages (65) toward the outer periphery ofthe screw rotor (40). Each of the screw-side oil supply passages (66)includes a body (66 a) and a plurality of lateral branches (66 b).

More specifically, as shown in FIG. 15, the body (66 a) of each of thescrew-side oil supply passages (66) is formed by a hole extending froman associated one of the axial passages (65) toward the outer peripheryof the screw rotor (40). In the third embodiment, the body (66 a) of thescrew-side oil supply passage (66) extends to an outer peripheralsurface (43) which helically extends between the helical grooves (41) ofthe screw rotor (40), and is opened at the outer peripheral surface(43). That is, the body (66 a) of the screw-side oil supply passage (66)is connected to an outer peripheral oil supply port (66 c) which is anoil supply port (4) opened at the outer peripheral surface (43) of thescrew rotor (40).

The lateral branches (66 b) are formed by holes extending from the body(66 a) toward the lateral faces (42 a. 42 b) of the helical groove (41),and are connected to groove's lateral oil supply ports (66 d) (in-grooveoil supply ports), which are the oil supply ports (4) opened at thelateral faces (42 a, 42 b) of the helical grooves (41). In thisembodiment, two lateral branches (66 b) are connected to a front portionand rear portion in the rotation direction of the body (66 a) of each ofthe screw-side oil supply passages (66). Thus, in this embodiment, atleast two groove's lateral oil supply ports (66 d) are opened at thefront lateral face (42 a) of the inner surface (42) of the helicalgroove (41) of the screw rotor (40) in the rotation direction, and twogroove's lateral oil supply ports (66 d) are opened at the rear lateralface (42 b). The diameter of each of the groove's lateral oil supplyports (66 d) and lateral branches (66 b) is determined so that thelubricant flows in such an amount that allows an oil film to be formedon the lateral faces (42 a. 42 b) of the helical groove (41) of thescrew rotor (40), and that the lubricant is kept from scattering in theshape of droplets.

The number of groove's lateral oil supply ports (66 d) and lateralbranches (66 b) is not limited to two, but may be less than two, or morethan two. In a preferred embodiment, the diameter is changed inaccordance with the number so that the lubricant flows in such an amountthat allows an oil film to be formed on the lateral faces (42 a, 42 b)of the helical groove (41) of the screw rotor (40), and that thelubricant is kept from scattering in the shape of droplets.

In this configuration, each of the screw-side oil supply passages (66)is connected to the groove's lateral oil supply ports (66 d) opened atthe lateral faces (42 a, 42 b) of the helical groove (41) of the screwrotor (40).

In a preferred embodiment, the screw-side oil supply passages (66) arepositioned such that the groove's lateral oil supply ports (66 d) areopened in the compression chamber (23) during the suction phase.Alternatively, the screw-side oil supply passages (66) may be positionedsuch that the groove's lateral oil supply ports (66 d) are opened in thecompression chamber (23) during the suction phase, and also in thecompression chamber (23) during the compression phase and the dischargephase.

As described above, in the oil supply mechanism (60) formed in the screwrotor (40), the axial passages (65) and the screw-side oil supplypassages (66) form a plurality of lubricant passages, each of which isbranched to have two or more outlets. Each of the lubricant passages hasan inlet which is opened in a space where the high pressure lubricantthat has lubricated the bearing (36), for example, is accumulated, andan outlet which is opened at the outer peripheral surface (43) of thescrew rotor (40) and the lateral faces (42 a. 42 b) of the groove.Therefore, due to the pressure difference between the inlet and outletsof the lubricant passage, the high pressure lubricant near the inletenters the lubricant passage, flows toward the outlet, and then flows tothe outer peripheral surface (43) of the screw rotor (40) and thelateral faces (42 a, 42 b) of the helical groove (41).

—Operation—

How the fluid is compressed in the compression mechanism (20) is thesame as in the first embodiment, and the description thereof is notrepeated. The oil supply operation different from that of the firstembodiment will be described below.

—Oil Supply Operation—

When the screw rotor (40) and the two gate rotors (50) rotate tocompress the refrigerant gas in the compression chamber (23), the oilsupply mechanism (60) formed in the screw rotor (40) supplies thelubricant to the sliding surfaces (3) of the two gate rotors (50) andthe screw rotor (40).

In the oil supply mechanism (60), as described above, the pressuredifference between the inlets and outlets of the lubricant passageformed by the axial passage (65) and the screw-side oil supply passage(66) causes the high pressure lubricant that has lubricated the bearing(36) and has been accumulated in a predetermined space to enter thelubricant passage, and flow toward the outlets. Specifically, the highpressure lubricant flows into the axial passages (65) serving as the oilsumps, flows into the plurality of screw-side oil supply passages (66)extending from the axial passages (65) toward the outer periphery by theeffect of the driving force derived from the pressure differencedescribed above and the centrifugal force generated by the rotation ofthe screw rotor (40), and then flows outward in the screw-side oilsupply passages (66) (see FIG. 15). The lubricant flowing through thescrew-side oil supply passages (66) flows from the outer peripheral oilsupply ports (66 c) to the outer peripheral surface (43) of the screwrotor (40), and also flows from the groove's lateral oil supply ports(66 d) to the lateral faces (42 a, 42 b) of the helical grooves (41) ofthe screw rotor (40).

The outer peripheral surface (43) of the screw rotor (40) provided withthe helical grooves (41) slides on the inner peripheral surface (30 a)of the cylindrical wall (30) covering the outer periphery of the screwrotor (40). Thus, lubrication is required to keep the outer peripheralsurface (43) of the screw rotor (40) and the inner peripheral surface(30 a) of the cylindrical wall (30) from seizing. On the other hand,when a gap is formed between the outer peripheral surface (43) of thescrew rotor (40) and the inner peripheral surface (30 a) of thecylindrical wall (30), the gap needs to be sealed so that the highpressure fluid does not leak to the low pressure side.

In the third embodiment, the screw-side oil supply passages (66) areformed in the screw rotor (40), and are connected to the outerperipheral oil supply ports (66 c) opened at the outer peripheralsurface (43) of the screw rotor (40) which slides on the cylindricalwall (30). In the screw rotor (40) configured in this manner, thelubricant in the screw-side oil supply passages (66) flows from theouter peripheral oil supply ports (66 c) to the outer peripheral surface(43) of the screw rotor (40) which slides on the inner peripheralsurface (30 a) of the cylindrical wall (30), thereby lubricating theouter peripheral surface (43), or sealing the gap, if any, between theouter peripheral surface (43) and the inner peripheral surface (30 a) ofthe cylindrical wall (30).

In the third embodiment, unlike the conventional configuration, theouter peripheral oil supply ports (66 c), which are the oil supply ports(4), are opened at the outer peripheral surface (43) of the screw rotor(40) that rotates. Therefore, the lubricant that has flowed from theouter peripheral oil supply ports (66 c) is rapidly spread over therotating screw rotor (40), and is quickly supplied to the slidingsurfaces (3) other than the outer peripheral surface (43) at which theouter peripheral oil supply ports (66 c) are formed. Further, since thescrew rotor (40) and the gate rotors (50) mesh with each other androtate together, the lubricant supplied to the screw rotor (40) israpidly spread to the gate rotors (50), and is quickly supplied to thesliding surfaces (3) of the gate rotors (50).

In the third embodiment, the screw-side oil supply passages (66) areformed in the screw rotor (40), and the oil supply passages (5) areconnected to the groove's lateral oil supply ports (66 d), which are thein-groove oil supply ports opened at the inner surface (42) of thehelical groove (41) of the screw rotor (66). In the screw rotor (40)configured in this manner, the lubricant in the screw-side oil supplypassages (66) flows from the groove's lateral oil supply ports (66 d) tothe lateral faces (42 a, 42 b) of the helical grooves (41) which slideon the gate rotor (50), thereby lubricating the lateral faces (42 a, 42b), or sealing the gap, if any, between the lateral faces (42 a. 42 b)and the gate rotor (50) sliding on the lateral faces. That is, in thethird embodiment, unlike in the conventional configuration, thelubricant is directly supplied to the lateral faces (42 a, 42 b), whichare the sliding surfaces (3), from the groove's lateral oil supply ports(66 d) opened at the lateral faces (42 a, 42 b) of the helical groovesof the screw rotor (40).

Further, in the third embodiment, unlike in the conventionalconfiguration, the groove's lateral oil supply ports (66 d), which arethe oil supply ports (4), are opened at the lateral faces (42 a, 42 b)of the helical grooves of the screw rotor (40) that rotates. Therefore,the lubricant which has flowed from the groove's lateral oil supplyports (66 d) is rapidly spread over the rotating screw rotor (40) by theeffect of the centrifugal force, and is quickly supplied to the slidingsurfaces (3) other than the lateral faces (42 a, 42 b) of the helicalgrooves. Further, the lubricant supplied to the lateral faces (42 a, 42b) of the helical groove of the screw rotor (40) also adheres to thegate rotors (50) which mesh with and rotate with the screw rotor (40),and is rapidly spread over the gate rotors (50) by the effect of thecentrifugal force. Thus, the lubricant is quickly supplied to thesliding surfaces (3) of the gate rotors (50).

Advantages of Third Embodiment

According to the configuration of the third embodiment described above,the screw-side oil supply passages (66) serving as the oil supplypassages (5) are formed in the screw rotor (40), which is at least oneof the screw rotor (40) and the gate rotors (50) mesh with each otherand rotate together, and the screw-side oil supply passages (66) areconnected to the outer peripheral oil supply ports (66 c) and thegroove's lateral oil supply ports (66 d), which are the oil supply ports(4) opened at the outer peripheral surface (43) and the groove's lateralfaces (42 a. 42 b). As a result, the lubricant is directly supplied fromthe outer peripheral oil supply ports (66 c) and the groove's lateraloil supply ports (66 d) to the outer peripheral surface (43) and thelateral faces (42 a, 42 b) of the helical grooves, which are the slidingsurfaces (3). Therefore, as compared to the conventional configurationin which the lubricant is injected from the oil supply port formed inthe cylindrical wall to be indirectly supplied to the inner surfaces(42) of the helical grooves of the screw rotor (40), the lubricant canbe reliably supplied in a smaller amount to the outer peripheral surface(43) and the lateral faces (42 a, 42 b), which are the sliding surfaces(3) of the screw rotor (40).

According to the third embodiment, unlike in the conventionalconfiguration in which the lubricant is injected from the oil supplyport formed in the cylindrical wall (30) which does not rotate, theouter peripheral oil supply ports (66 c) and the groove's lateral oilsupply ports (66 d), which are the oil supply ports (4), are opened atthe outer peripheral surface (43) and the lateral faces (42 a, 42 b) ofthe helical grooves, which are the sliding surfaces (3) of the screwrotor (40) that rotates, so that the lubricant flows to the slidingsurfaces (3) from these oil supply ports. Therefore, the lubricant thathas flowed from the outer peripheral oil supply ports (66 c) and thegroove's lateral oil supply ports (66 d) is rapidly spread over therotating screw rotor (40), and can be quickly supplied to the slidingsurfaces (3) other than the outer peripheral surface (43) and thelateral faces (42 a, 42 b) of the helical grooves at both of which theoil supply ports (4) are formed. Since the screw rotor (40) and the gaterotors (50) mesh with each other and rotate together, the lubricantsupplied to the screw rotor (40) is rapidly spread to the gate rotors(50), and can be quickly supplied to the sliding surfaces (3) of thegate rotors (50).

As described above, in the third embodiment, the efficiency of thecompressor is not lowered because it is unnecessary to increase thepower for the transport of the lubricant and the power for the rotationof the screw rotor (40), unlike the conventional configuration in whicha large amount of lubricant is supplied. Supplying the lubricant in asmall amount to at least one of the sliding surface (3) of the screwrotor (40) or the sliding surface (3) of the gate rotor (50) makes itpossible to lubricate the sliding surface (3) of each of the screw rotor(40) and the gate rotor (50), or to seal a gap, if any, between thesliding surface (3) and its counterpart sliding surface. That is,according to the third embodiment, the sliding surfaces (3) of the screwrotor (40) and the gate rotor (50) can be kept from seizing, and thehigh pressure fluid can be blocked from leaking from the compressionchamber, even if the supply amount of the lubricant is reduced.Therefore, in the third embodiment, the supply amount of the lubricantcan be reduced without lowering the reliability of the screw compressor(1), which can improve the compressor efficiency.

According to the third embodiment, the axial passages (65) serving asthe oil sumps are formed at a position closer to the rotation axis ofthe screw rotor (40) than the bottom faces (42 c) of the helical grooves(41), and base ends of the screw-side oil supply passages (66) arerespectively connected to the axial passages (65). That is, thescrew-side oil supply passages (66) extend from the axial passages (65)in the screw rotor (40) toward the outer periphery. In thisconfiguration, the screw rotor (40) rotates to generate the centrifugalforce, which causes the lubricant to enter the screw-side oil supplypassages (66) from the axial passages (65), flows toward the outerperiphery of the screw rotor (40), and flows from the oil supply ports(4) (the outer peripheral oil supply ports (66 c) and the groove'slateral oil supply ports (66 d)) to the sliding surfaces (3) of thescrew rotor (40) (the outer peripheral surface (43) and lateral faces(42 a, 42 b) of the helical grooves). That is, this simple configurationcan supply the lubricant to the sliding surfaces (3) of the screw rotor(40) (the outer peripheral surface (43) and the lateral faces (42 a, 42b) of the helical grooves) by utilizing the centrifugal force generatedby the rotation of the screw rotor (40).

OTHER EMBODIMENTS

In the first to third embodiments, the single-screw compressor providedin the refrigerant circuit to compress the refrigerant has beendescribed. However, a target to be compressed (fluid) is not limited tothe refrigerant, and the compressor is not limited to the single-screwcompressor. The compressor may be a twin screw compressor including amale rotor and a female rotor, or a compressor including female rotorsprovided on both sides of a male rotor.

The front oil supply ports (63 c) that have been formed in the first andsecond embodiments may not be formed. Alternatively, the lateral oilsupply ports (63 b) may be omitted, and the gate-side oil supplypassages (63) may be connected only to the front oil supply ports (63c).

In the first and second embodiments, it has been described that thelateral oil supply ports (63 b) of each of the gate-side oil supplypassages (63) are opened at the side surfaces (51 a, 51 b) of the gate(51) on the front and rear sides in the direction of rotation of thegate (51). However, the lateral oil supply ports (63 b) may be opened atleast at the rear side surface (51 b) of the gate (51), and no oilsupply port may be opened at the front side surface (51 b) of the gate(51). The rear side surface (51 b) in the rotation direction of the gate(51) is the sliding surface (3) which reliably slides on the screw rotor(40) and is pressed by the screw rotor (40), and therefore, is probablyworn through the sliding movement. However, the lateral oil supply ports(63 b) opened at the rear side surface (51 b) cause the lubricant to bereliably supplied between the rear side surface (51 b) and the lateralface (42 a, 42 b) of the helical groove (41). This can protect the gate(51) and the screw rotor (40) from the sliding wear.

Similarly, in the third embodiment, the groove's lateral oil supplyports (66 d) of the screw-side oil supply passages (66) are opened atboth lateral faces (42 a, 42 b) of each of the helical grooves (41) ofthe screw rotor (40) on the front and rear sides in the rotationdirection of the screw rotor. However, the groove's lateral oil supplyports (66 d) may be opened at least at the lateral face (42 b) on therear side of the helical groove (41) in the rotation direction, and nooil supply port may be opened at the lateral face (42 a) on the frontside of the helical groove (41) in the rotation direction. The rearlateral face (42 b) of the helical groove (41) in the rotation directionis the sliding surface (3) which reliably slides on the gate (51) of thegate rotor (50) and presses the gate (51) of the gate rotor (50), andtherefore, is probably worn through the sliding movement. However, thegroove's lateral oil supply ports (66 d) opened at the rear lateral face(42 b) of the helical groove (41) cause the lubricant to be reliablysupplied between the rear lateral face (42 b) of the helical groove (41)and the gate (51) of the gate rotor (50). This can protect the gate (51)of the gate rotor (50) and the screw rotor (40) from the sliding wear.

Further, in the first and second embodiments, four lateral oil supplyports (63 b) are opened at each of the side surfaces (51 a, 51 b) of thegate (51) at substantially equal intervals from the base end to distalend of the gate (51). However, it is not always necessary to provide aplurality of lateral oil supply ports (63 b) at equal intervals, and atleast one lateral oil supply port (63 b) may be formed at a positioncloser to the base end of the gate (51) than the center thereof in theradial direction. The at least one lateral oil supply port (63 b) openedat a position closer to the base end of the gate (51) than the centerthereof in the radial direction makes it possible to supply thelubricant to the base end of the side surface (51 a, 51 b) of the gate(51), and to easily spread the lubricant toward the distal end of theside surface (51 a, 51 b) of the gate (51) by utilizing the centrifugalforce. This configuration can minimize the number of the lateral oilsupply ports (63 b), and can further reduce the supply amount of thelubricant.

Similarly, in the third embodiment, two groove's lateral oil supplyports (66 d) are opened at each of the lateral faces (42 a. 42 b) of thehelical grooves (41) of the screw rotor (40). However, the two groove'slateral oil supply ports (66 d) are not always necessary, and at leastone groove's lateral oil supply port may be formed at each lateral face(42 a, 42 b) of the helical groove (41) at a position closer to thebottom face (42 c) of the helical groove (41) than to the outerperipheral surface (43) of the screw rotor (40). The at least onegroove's lateral oil supply port (66 d) opened at the lateral face (42a, 42 b) of the helical groove (41) of the screw rotor (40) at aposition closer to the bottom face (42 c) of the helical groove (41)than to the outer peripheral surface (43) makes it possible to supplythe lubricant to a portion of the lateral face (42 a) of the helicalgroove (41) closer to the rotation axis, and to easily spread thelubricant to a portion of the lateral face (42 a, 42 b) of the helicalgroove (41) closer to the outer peripheral surface (43) by utilizing thecentrifugal force. This configuration can minimize the number of thegroove's lateral oil supply ports (66 d), and can further reduce thesupply amount of the lubricant.

Further, in the first and second embodiments, the oil supply mechanism(60) having the gate-side oil supply passage (63) has been provided ineach of the two gate rotors (50). However, the oil supply mechanism (60)may be provided in only one of the gate rotors (50). When the oil supplymechanism (60) provided in one of the gate rotors (50) supplies thelubricant to the sliding surfaces (3) of the gate rotor (50) and thescrew rotor (40), the lubricant adheres to the lateral faces (42 a, 42b) of the helical grooves (41) of the screw rotor (40). Thus, when theamount of the lubricant that adheres to the lateral faces (42 a, 42 b)of the helical grooves (41) of the screw rotor (40) is controlled, thelubricant can be left in the helical grooves (41) to lubricate thesliding surfaces (3) of the other gate rotor (50) and the screw rotor(40), and to seal the gap between the sliding surfaces (3).

In the first and second embodiments, the gate-side oil supply passages(63) of the oil supply mechanism (60) are formed in all the gates (51)of the gate rotor (50). However, the gate-side oil supply passage (63)may be formed in at least one of the gates (51), and more preferably,may be formed in the same number as the number of helical grooves (41)in the screw rotor (40) (six in the above-described embodiments) in thegates (51) adjacent to each other. When the amount of lubricant suppliedfrom the gate-side oil supply passages (63) to the sliding surfaces (3)of the gate rotor (50) and the screw rotor (40) is controlled byadjusting the number and diameter of the lateral oil supply ports (63b), the sliding surfaces (3) of the gate rotor (50) and the screw rotor(40) can be protected from the seizing even if the gate-side oil supplypassage (63) is not formed in every gate (51).

In the first and second embodiments, the right oil supply mechanism (60)in FIG. 3 has the in-shaft communication passage (61) formed inside thefront shaft portion (58 a), and the left oil supply mechanism (60) hasthe in-shaft communication passage (61) formed inside the rear shaftportion (58 b). However, the position of the in-shaft communicationpassage (61) is not limited thereto. The right oil supply mechanism (3)in FIG. 3 may have the in-shaft communication passage (61) formed insidethe rear shaft portion (58 b), and the left oil supply mechanism (60)may have the in-shaft communication passage (61) formed inside the frontshaft portion (58 a). Alternatively, both of the oil supply mechanisms(60) may have the in-shaft communication passage (61) formed inside thefront shaft portion (58 a) or the rear shaft portion (58 b).

In the third embodiment, the screw-side oil supply passages (66) areconnected to the outer peripheral oil supply ports (66 c) opened at theouter peripheral surface (43) of the screw rotor (40) and the groove'slateral oil supply ports (66 d) opened at the lateral faces (42 a. 42 b)of the helical grooves (41). However, the screw-side oil supply passages(66) are not limited to those connected to the outer peripheral oilsupply ports (66 c) and the groove's lateral oil supply ports (66 d).For example, the screw-side oil supply passages (66) may be connected tobottom oil supply ports which are opened at the bottom faces (42 c) ofthe helical grooves (41) of the screw rotor (40). Alternatively, thescrew-side oil supply passages (66) may be connected only to the outerperipheral oil supply ports (66 c) or the groove's lateral oil supplyports (66 d).

The switching mechanism (6) of the second embodiment is not limited tohave the above-described configuration, and may be configured in any wayas long as the gate-side oil supply passages (63) can be switchedbetween the supply state and the non-supply state. Further, theswitching mechanism (6) of the second embodiment can be applied to theoil supply mechanism (60) formed in the screw rotor (40) as described inthe third embodiment. In this case, a closing portion as described inthe second embodiment may be provided in a space in which the dischargeends of the plurality of axial passages (65) are opened and the highpressure lubricant is accumulated.

The embodiments described above are merely exemplary ones in nature, anddo not intend to limit the scope of the present invention, applications,or use thereof.

INDUSTRIAL APPLICABILITY

As can be seen from the foregoing, the present invention is useful for ascrew compressor.

DESCRIPTION OF REFERENCE CHARACTERS

-   -   1 Single-Screw Compressor (Screw Compressor)    -   3 Sliding Surface    -   4 Oil Supply Port    -   5 Oil Supply Passage    -   6 Switching Mechanism    -   23 Compression Chamber    -   30 Cylindrical Wall (Rotor Casing)    -   39 Opening    -   40 Screw Rotor (First Rotor)    -   41 Helical Groove    -   42 Inner surface of Helical Groove (Sliding Surface)    -   42 a Lateral Face of Helical Groove (Sliding Surface)    -   42 b Lateral Face of Helical Groove (Sliding Surface)    -   43 Outer Peripheral Surface (Sliding Surface)    -   50 Gate Rotor (Second Rotor)    -   51 Gate    -   51 a Front Side Surface (Side Surface, Sliding Surface)    -   51 b Rear Side Surface (Side Surface, Sliding Surface)    -   51 c Front Surface (Sliding Surface)    -   52 Coupling Portion    -   55 Support Member    -   63 Gate-side Oil Supply Passage (Oil Supply Passage)    -   63 b Lateral Oil Supply Port (Oil Supply Port)    -   63 c Front Oil Supply Port (Oil Supply Port)    -   65 Axial Passage (Oil Sump)    -   66 Screw-side Oil Supply Passage (Oil Supply Passage)    -   66 c Outer Peripheral Oil Supply Port (Oil Supply Port)    -   66 d Groove's Lateral Oil Supply Port (Oil Supply Port,        In-Groove Oil Supply Port)

1. A screw compressor, comprising: a first rotor provided with a helicalgroove; a second rotor meshing with the first rotor, the second rotorrotating together with the first rotor; and a rotor casing covering atleast an outer periphery of the first rotor, the rotor casing defining acompression chamber in the helical groove together with the first rotorand the second rotor, a fluid being compressible in the compressionchamber, and at least one of the first rotor or the second rotor beingis provided with an oil supply passage connected to an oil supply portopened at a sliding surface of the rotor to supply a lubricant to thesliding surface.
 2. The screw compressor of claim 1, further comprising:a switching mechanism configured to switch the oil supply passagebetween a supply state in which the lubricant is supplied to the slidingsurface and a non-supply state in which no lubricant is supplied to thesliding surface.
 3. The screw compressor of claim 2, wherein theswitching mechanism is further configured to switch the oil supplypassage to the supply state by causing an oil supply source tocommunicate with the oil supply passage when a rotational angle positionof the rotor provided with the oil supply passage is in a predeterminedangular range, and to switch the oil supply passage to the non-supplystate by blocking the oil supply source from the oil supply passage whenthe rotational angle position of the rotor is out of the predeterminedangular range.
 4. The screw compressor of claim 1, wherein the firstrotor is a screw rotor rotatably housed in a cylindrical wallconstituting the rotor casing, the second rotor is a gear-shaped gaterotor having a plurality of flat gates, the second gate rotor isarranged outside the cylindrical wall, and some of the gates enter aspace inside the cylindrical wall via an opening formed in thecylindrical wall and mesh with the screw rotor so that the gate rotorrotates together with the screw rotor, the oil supply passage is formedin at least one of the gates of the gate rotor, and the oil supply portis a lateral oil supply port opened at a side surface of the at leastone gate, and the side surface serves as the sliding surface whichslides on the screw rotor.
 5. The screw compressor of claim 4, whereinthe lateral oil supply port is opened at least at the side surface on arear side in a direction of rotation of the at least one gate.
 6. Thescrew compressor of claim 4, wherein the oil supply passage is connectedto a front oil supply port opened at a front surface of the at least onegate facing the compression chamber.
 7. The screw compressor of claim 4,wherein the lateral oil supply port includes at least one lateral oilsupply port formed at a position closer to a base end of the at leastone gate than a center of the at least one gate, in a radial directionof the gate rotor.
 8. The screw compressor of claim 4, furthercomprising: a support member supporting the gate rotor from a rear sideopposite to the compression chamber; and an oil sump formed between thesupport member and a coupling portion of the gate rotor coupling baseends of the plurality of gates, the oil sump being configured to havethe lubricant supplied thereto, wherein the oil supply passage extendsin a radial direction of the gate rotor of the at least one gate, andhas a base end connected to the oil sump.
 9. The screw compressor ofclaim 1, wherein the oil supply passage is formed in the first rotor,and the oil supply port is an in-groove oil supply port opened at aninner surface of the helical groove serving as the sliding surface ofthe first rotor sliding on the second rotor.
 10. The screw compressor ofclaim 1, wherein the oil supply passage is formed in the first rotor,and the oil supply port is an outer peripheral oil supply port opened atan outer peripheral surface of the first rotor serving as the slidingsurface of the first rotor sliding on the rotor casing.
 11. The screwcompressor of claim 9, wherein the first rotor has an oil sump formed ata position closer to a rotation axis of the first rotor than a bottomface of the helical groove, the oil sump being configured to have thelubricant supplied thereto, and the oil supply passage extends from theoil sump toward an outer periphery of the first rotor.
 12. The screwcompressor of claim 10, wherein the first rotor has an oil sump formedat a position closer to a rotation axis of the first rotor than a bottomface of the helical groove, the oil sump being configured to have thelubricant supplied thereto, and the oil supply passage extends from theoil sump toward an outer periphery of the first rotor.
 13. The screwcompressor of claim 2, wherein the first rotor is a screw rotorrotatably housed in a cylindrical wall constituting the rotor casing,the second rotor is a gear-shaped gate rotor having a plurality of flatgates, the second gate rotor is arranged outside the cylindrical wall,and some of the gates enter a space inside the cylindrical wall via anopening formed in the cylindrical wall and mesh with the screw rotor sothat the gate rotor rotates together with the screw rotor, the oilsupply passage is formed in at least one of the gates of the gate rotor,and the oil supply port is a lateral oil supply port opened at a sidesurface of the at least one gate, and the side surface serves as thesliding surface which slides on the screw rotor.
 14. The screwcompressor of claim 3, wherein the first rotor is a screw rotorrotatably housed in a cylindrical wall constituting the rotor casing,the second rotor is a gear-shaped gate rotor having a plurality of flatgates, the second gate rotor is arranged outside the cylindrical wall,and some of the gates enter a space inside the cylindrical wall via anopening formed in the cylindrical wall and mesh with the screw rotor sothat the gate rotor rotates together with the screw rotor, the oilsupply passage is formed in at least one of the gates of the gate rotor,and the oil supply port is a lateral oil supply port opened at a sidesurface of the at least one gate, and the side surface serves as thesliding surface which slides on the screw rotor.